Is it OK to put the trap for a shower on the horizonal run instead of the initial vertical drop from the drain? What I'd like to do is turn the initial drop through the joist with a 90. Once on the other side, go with another 90 into the trap. The vent would only be about a foot away from this point. The trap/vent relationship should be OK. I'll try some ASCII art.
--------------------- Subfloor | J | J | Joist --------------| |---------Vent |----| Trap
Al