I think I'd like to go with S&D PVC for my new setup, especially since it would be the easiest to make my own gates with. I have a few unknowns to figure out. Like, what sizes does S&D PVC come. I'm sure there is 4" and 6". Anything smaller is useless, what about larger? 7"? 8"?
I have another concern as well. The inlet to the new DC is square and they supplied me with a square to 7" round coupling, if I go to PVC after that, how well do the sheetmetal fittings marry with S&D PVC. Is it too big, too small, or just right?