That is cool...quite simple but i would have never thought to use PVC...You could also add some padding to it...insulation roll.
I guess padding would be OK but I’ve seen no reason for it. The tolex s strong enough to handle being carted around in the back of a pickup and in a trailer for years, sitting on PVC won’t even be noticed. Tubular water pipe insulation wouldn’t be expensive, and would work fine, easily available too.
Not hard to make, and I wouldn’t worry about setting an amp twice the weight of the Champ or Pro Jr on it at all. If I wanted one for a bigger amp I’d use 3/4” or 1” PVC and use an added strut in the middle for support. If you decide to make one, fit everything together before gluing, be careful taking measurements, and sit each section on a flat surface to assemble to keep everything straight and square. Assemble in sections then put them together.
I left the front legs with no glue so I can remove them later and replace with longer or shorter legs if I need to. So far these have been perfect, standing 8 feet in front of the amp it’s pointed right at my ears where it needs to be, not at my knees. They don’t have ears. Also works great onstage, I can hear myself lots better and don’t have to use a chair to sit the amp on, and it weighs nothing, a few ounces. Fender Amp Field Guide says the Champ weighs 20lbs, same for Pro Jr.
It could also be painted black, I didn’t bother. I did use clear PVC cleaner to remove all the black print markings. I use it at home, in the practice room and onstage, my Pro Jr is sitting on it right now.