Anchorengineer:
Why not contact some PVC Pipe people and see what they prefer, as one possible solution to the problem. They may have some literature, testing and experience which you can hang your hat on. I would think that the PVC pipe will wear and abrade against a steel bearing pl., more so than steel on steel. And, for that reason I would wonder if you might not use a thin steel pl., shaped to the o.d. of the pipe, and bond it to the pipe at each bearing location; and that shaped pl. then mates with a saddle on the support structure. I think a saddle, as SRE suggests, is a vast improvement over a flat bearing/support pl. (top of a beam flg.). The saddle provides some load distribution to the pipe, and provided some lateral support too.
The GC wants the cheapest, quickest solution, that’s money in his pocket. And, he’ll be long gone when someone has to start dealing with the pipe wear and damage, or lateral movement. And, if you can find him, he’ll say the EOR accepted what I did, so it’s really his fault that he didn’t make me do it right in the first place.