The video shows the cutout and frame from the inside. It's worth a look.

The top is cut behind the 1st brace and about 4" above the gutter, per instructions received from the van top vendor. The seats are in front of the first brace, so you can't really stand up there anyway. This gives support and protection to the driver and passenger. I cut it using a combination of electric sheet metal shears and a cut-off wheel. (HF 68199 and 68523)

The metal removed from the top weighed a bunch! Probably around 100 lbs.

After looking around my garage and knowing what I could do, I decided to either make a frame out of 1/4-1/8" plywood strips 1-1/2" wide glued together so I could make bends, or use some 1'1/2" .06 wall 6061-T6 aluminum tubing. The tubing was used. Bent with a tubing bender and 1-1/2" dies (JMR Sportsman or JD Squared model JD 3)



Wherever the tubing was bent, it was annealed with a propane torch, to burn off the heat treating markings and slowly bent in a hydraulic tubing bender with 1-1/2" dies. Plywood bent and glued would work just as well, as also would wooden (clear (without knots) is best) 2x2's with plywood gussets for the corners.

It just so happens that closet pole, 1-3/ 8 fits nicely inside the 1-1/2 .06 wall tubing Anywhere a piece need help (short or boo boo), I used the pole to help. An 1-1/2" hole saw, in a drill press allowed cutting the tubing to fit each other. Where the tubing met the body, the closet pole was fit to the body, then inserted into the tubing, and a sheet metal screw or two were used to lock it in.

I made the first side, then the second side, to match. I was a little off (1") and if you look close you can see it.

To hold the two sides, I made a 12" piece of panelling, cut to approx. what I wanted and screwed it in the rear, one side at a time, on this you could use a helper. After a couple of adjustments, the front and side panels were attached.

It's a good idea to step back and look at things every so often and fix weird stuff (sagging, crooked) before it gets harder to fix. Braces 2 feet on center give you good nailing spaced when you go to panel the inside.

For the roof, I bent braces to be more aerodynamic and to allow for a higher ceiling and put a place to install a roof vent or A/C.

The round corners posed an issue, but I either cut kerfs in the panelling or used spray foam to provide a rounded surface for finishing. (Fiberglass needs a 3/8 or greater radius or it bubbles.)