To clarify, the trap arm (from trap outlet to vent connection) needs to be sloped at least 1/4" per foot, but also may fall no more than one pipe diameter. That's to avoid the possibility of siphoning the trap. So you could slope the trap arm at more than 1/4" per foot, but that reduces how far you can go before hitting the one pipe diameter drop limit.
Ok, and are there any restrictions as to how long the wet vent can be?
I'll need to bring it through the wall for about 4 feet, then down into the floor to connect to the shower drain with a wye fitting.
Is it ok to have sharp turns in the wet vent or anything like that?