I used 'full extension' heavy duty drawer glides for my wheel to slide in my pit. They are strong enough to support the weight of the wheel, plus the much heavier stress of me yanking on the thing when I am racing... especially when things aren't going my way! You can also look for server racking gear. It is generally heavy duty stuff.
I had promised a while back some info on the sprung load latches I was using... well, I finally remembered to swing by the hardware store and snap a pic for you.
I have seen them called chain bolts and spring bolts. Just make sure it has a spring that keeps it in the closed position unless you pull the chain. I replace the chain with braided metal cable.
In reference to your question about using PVC for your framework. I just recently finished building a setup for a friend of mine based on some plans he found on the internet.
I think it came out as good as it could, but we both agree it is a bit... wiggly... especially when doing agressive flying. He doesn't have a wheel set up, but I don't think I would relish bolting a wheel on to it as well. The PVC just flexes too much and doesn't have enough mass to it to make it feel solid. We have discussed filling the piping with sand or expanding foam insulation, but we're not sure it would help much. We may end up using it as a framework to start attaching an MDF skin to, but if we were starting from scratch, we would skip the PVC all together.
By the way, he is using Velcro to strap the chair to the rig whenever he flys. It keeps him from sliding away from the controls, but he forgot to unstrap himself once and almost broke one of the supports when he went to slide away and stand up. The Velcro holds nice and tight though!
Hope all this helps!