I selected Motion Windows because because:

The windows are sliders and can be opened while driving
The screens are easily removed and I can pass the showerhead out through the side window for the outdoor shower
The Motion Windows build quality is really good – quarter inch glass, factory tint, aluminum mesh screens, durable locking mechanism.

I purchased two large windows for the sliding door and behind the driver’s seat, and two smaller windows for above the high rear bed.

I had planned on installing the Windows myself, but an install slot became available the day I was going to pick them up in Vancouver Washington, and I opted for having them do the install at $125 per window. I figure it would've taken me two solid days, and it took them four hours. And they were responsible for cutting four giant holes in the side of my brand-new van :-)

The aluminum screens are easily removed.

The trim ring which clamps the window to the van sheet metal.

I took some photos during the install process, and George was kind enough to let me help out along the way. So here's how it's done.

And there’s another blog on this, as well as a video here.

Materials and tools

The windows from Motion Windows
Sharpie for layout
Cardboard to make templates for each size of window
Measuring tape
Framing square
Metal file to clean up the rough edges
Jigsaw with a metal cutting 32 TPI blade. You could use a 24 TPI blade, but you’ll get less chatter on the sheet metal with a finer blade.
Drill with 3/32” bit for pilot holes
4.5” angle grinder with a metal cutting blade to create a hole for the jigsaw (could use a 3/8” drill bit instead)
Measuring tape, and a couple of flexible metal rulers or aluminum bars make drawing lines behind the bracing easier
Markel Paint Marker is quite a bit easier than a q-tip and bottle of paint, and you’ll use it elsewhere in your project.
Blue painters tape for masking off the exterior of the van
An old blanket to tarp off the interior of the van
Duct tape to hold the metal in place when cutting out the opening

Steps

Layout the interior

Make an accurate lightweight cardboard circle of the appropriate corner radius. Mine required 2 1/2” radius.
Unscrew the trim ring from the window. Note the location of the screws, and how they fit into the channel of the window, as this is where you will be placing the final screws at the end of installation.
Make a template of the opening by placing the window on top of a piece of cardboard. Trace around the part of the window that will go in through the hole in the side of the van. DO NOT trace around the outside of the entire window :). The red arrow points to this inner part of the window which you trace onto cardboard.
Using your cardboard template, decide exactly where to place the windows.
1. The transit has some areas allocated for windows, but there is some flexibility in placement of the Motion Windows within this space. For the larger window, you’re limited to a bit of movement left and right. For the smaller windows, there’s a lot more flexibility.
2. The cut line cannot be too close to the panel braces or framing. Refer to the pics below for the closest you can get to the top and sides of the Transit window indents. In general, within 1” of the left/right bracing, and maybe 3/4” from the top bracing.
Put down the cardboard template. It’s useless for actually doing the layout, as the bracing pushes it away from the sheet metal. Using a measuring tape, mark the left and right edges of the opening, and then mark the top and bottom edges. Add about 3/16” of space all around - so that after the window is placed in the hole you can make a small adjustment left/right/top/bottom to level it out. For example, if the window height is 23 7/8, the hole height should be 24 1/4. The top and bottom edges are parallel to each other. Use a square to square up the left/right lines and the top/bottom lines. Use a straight edge to make the long lines.
Once you have the lines marked, use the radius template to make the curved corners.
Measure everything again. Measure all of the lines again. Measure the windows again. Make sure all of your corners are square except on the forward edge of the big windows. Hold the cardboard template up to the window, and make sure it matches exactly. Now hold the cardboard template up to your markings on the van wall, and make sure they match.
Once you are really 100% certain everything is laid out correctly, go inside and watch tv. Then go back out and measure again. You only have one shot at cutting giant holes in your van.

Trace around the inner part of the window onto cardboard

This is the window behind the driver’s side. It’s placed as far forward as possible. The top, left, right, and bottom edges have been measured and marked. Now George is connecting the lines.

Applying a radius to the corners using the radius template. Note that for the rear window we are partially cutting into the brace, but the trim can slip underneath this after the bonding foam is scraped out.

Layout the exterior

Drill pilot holes to transfer the interior markings to the exterior

Marking where the internal bracing is locati. Area is fully masked off, including the sheet metal ridge below which can catch hot metal.

Now it’s time to transfer your inside layout to the exterior. It’s too hard to cut the van wall accurately from the inside with all of the bracing in place.

An old blanket taped along the top and bottom edges of the opening keeps the metal fragments out of the interior spaces where it’s impossible to remove later.

Using your 3/32” drill bit, drill a total of 8 pilot holes for each window - 2 pilot holes at each corner. You’ll use these to draw both the straight lines and the curves on the exterior of the van. Try to catch the metal fragments with your hand, or run a shop vac while you’re drilling.
Repeat the process of using the straightedge and radius template to mark up the cut line on the exterior of the van
Mask off the exterior to protect the finish from hot metal landing on it.
Using the cardboard template, mark up where the interior bracing is location. You’ll need this when making your cuts to cut these areas before the end.

Cut giant holes in your van

Here’s where all of your triple measuring pays off. You are going to nonchalantly cut giant holes in your van.

George cutting around. Note the markings indicating the interior bracing.

Tape up a blanket inside the van around the window. The blanket will catch all the hot metal fragments.
Using a grinder or drill, make a hole at the bottom left and right sides of each window opening, inside your line. You’ll use this to insert the jigsaw blade into to start your cut. If you’re using a grinder, consider your spark path, and maybe throw a towel over the rear view mirror.
Start cutting along the line with the jigsaw. Go as slow as necessary to make a nice straight cut.
Here’s something George taught me - to avoid the dreaded sheet metal shimmy which can drive your cut off course or make it really ragged, follow these steps:
1. Cut the sides first
2. Cut along the bottom and top corners next
3. Cut through any bracing
4. Put duct tape along a long cut to keep in from vibrating
5. Leave a small amount of metal in 4 locations - 2 spots on the top, 2 spots on the bottom. And have tape to hold the metal in place for the last 4 cuts
6. Cut through the last two sections on the bottom
7. Cut through the last two sections on the top (the top is least prone to vibration because of it’s proximity to the bracing)
8. Use a file to clean up the rough edges of the cut and knock down any jaggies from the pilot holes.
9. Use the paint marker to paint the edges

Congratulations! You now have giant holes in your van!

Install the windows

The slider door lock will bump into the window. You’ll need to cut off about 1”. I used a pair of wire cutters, but an angle grinder might be cleaner.
Insert the trim ring on the interior of the vehicle around the opening. It’s easiest if you insert the top part of the trim ring underneath the cut off framing members, and then finish with the bottom side.
Open the sliding glass portion of the window, this makes it easier to handle the window.
Insert the window into the opening and verify that it’s a close fit all the way around.
With the window lying outside down on a soft surface, clean the window flange with some lacquer thinner. Then apply the seal tape on the flange starting at the middle of the bottom of the window, going all the way around, and overlapping the two ends by approximately ½ inch. Pull the backing from the tape as you progress to make the transition around the corners easier.
Use a spray water bottle and mist the perimeter of the opening on the outside of the vehicle. This prevents the tape from sticking to the outside wall before you’re satisfied with the final position of your new window.
The final installation of the window is easier if you have someone helping you. Place the window with the foam tape into the opening and make sure it is parallel to the van sheet-metal indentation along the top edge. This is the most noticeable joint where an offkilter placement would be obvious.
The person on the outside holds the window in place, pressing it against the side of the vehicle, while the person on the inside screws the trim ring into the window frame.
Even after the trim ring is partially screwed down you can still tweak the window location if it shifted.
Motion Windows says that no additional sealant is needed, so I didn’t apply any. Seems like caulk would end up peeling and looking ugly after a few years.
Wash off the side of your van to make sure there are no hot metal particles stuck to the paint
Step back and admire your handiwork!