Tom - Thanks for your comments. I think the ambiguity in the drawing I got was done so that they would have some flexibility in how they wanted to do it "on the fly" - pretty much like what it sounds like you're saying. It's cool that you've been able to make comparisons with other houses that are the same model. I imagine the trunk placement and furnace placement is probably set in stone in my build (so they can do 100 other same model homes the same way), but the other runs vary some.
I'm hoping to become chummy with the super, and maybe my desires can steer *something* down the road. Reworking the HVAC runs later - I don't think should be impossible, even if it costs some money. I haven't even seen what the joist bays look like w/LVL joists, so I'm curious. Probably nothing different than any other normal dimensional lumber joists. Wonder if you can run ANYTHING through LVL, like electrical? I should read up..
Completely understand about the ceiling height and code..... I understand the reasons for the code, but it's a challenge to get everything else to all work together too!
I found myself scared, looking at the original design, thinking the runs were 8", but the runs that criss-cross are almost all 6". Maybe I'm being anal about height though. I just felt strongly about it, because you can't realistically change it once it's built.