I've used PVC for enclosures in the past and didn't seem to have any
trouble. But I noticed that on a couple projects we had a couple
things that started to bend from thermal expansion. The sunny side of
the free standing vertical piece heats more than the shadow side, and
the differing expansion rate creates a bend. Even for a 5' piece, it
seemed fairly extreme. But then other times this hasn't happened. We
were using the special furniture grade PVC in 1" size. Anybody had any
experience with this or come up with any solutions? Notice any
difference between PVC types or anything?

Thanks for any help,