I...Grigg on these forums built a simple canopy/enclosure for a 1-ton pickup from PVC pipe and plastic tarpaulins. Worked pretty good.
It was only just OK.. it was also about 17 years ago, I had a lot to learn and hadn't seen anything like the ones discussed here or I would have done a better job back then.
Mine was just 4 pieces of EMT conduit (metal) bent into U shapes that fit in the stake pockets, shimmed with little blocks of wood to take up the extra space in the stake pocket.
The cover was a tan vinyl truck tarp custom made to my dimensions and with D rings appropriately placed for bungy cord use. The cover/tarp could also be folded in and cover the bed level with the top, no hoops in place. I never tried but didn't feel like it would travel well assembled. Did use the tarp/cover flat over the bed when it was going to rain on a drive.
Dug up a few old pictures, it really wasn't very fancy.. It also wasn't very tall, should have been taller and with more square corners.
Don't have a good picture with it all assembled but you can get the idea. One picture of the tarp with no hoops after driving in the darkest thunderstorm I can remember, that picture driving down the road is mid afternoon, looks like night.
Used that cover for a month driving around the country coast to coast sleeping in the bed of the truck several days at a time then a hotel occasionally for shower and such. Then only used it a few more times for camping trips. Now I still use the tarp as a tarp with other vehicles.
I've enjoyed seeing these production made canvas bed covers/frames. Thanks for sharing.
Grigg