Building a PVC pit frame and looking for suggestions

[Qbot2640]

I will second the info about PVC being saggy and requiring constant repainting. I don't know if this is the right choice for you - but we used electrical conduit and it is working great. We were able to fabricate corners that the long sections attach to with thumbscrews - and instead of painting we covered our with colored duct tape. Two years - seven FRC events, plus tons of demonstrations and the pipes still look great. Plus, the conduit (we used half-inch) is much more compact and easier to set up and tear down.