I made one once
I have built a lot of boats and usually buy them but made one once. I’ll give you a general description.
I used exercise mat bought at Walmart. I heated and bent some window replacement plexiglass and contacted cemented on the mat material. The plexi had some long slots I cut in it to weave the web strap in and out of it before I glued the mat on it. Then I covered the entire thing with black (polyester) fabric I had but you can buy at a fabric store. I basically glued that to the mat and plexi with contact cement. Done! The web straps can be screwed or put into a slot on the sides of the boat. It actually came out almost as nice as commercial ones. I actually had all the ingredients so It only cost me some labor.
I use a 12" piece of PVC and
slip a 12" piece of pool noodle over it. The strap and bungee that hold it in place run through the PVC.
I have done this on two boats and find it to work well for me.
I just got a One Ocean Cirrus
The guy who built it did an outstanding job. He curved a piece of plywood and backed it with carbon fiber. If your interested send me a private email with your email address and I’ll send some photos.