Geberit venting
I'm doing this right now and had roughed my closet bend for a 3 1/2" from center of the closet riser to the leading edge of the bottom plate this would allow you to install a 3" X 2" wye if framing is roughed using 2" X 6" and break a 45 into the back of the 2" X 6" behind the carrier and up. I'm planning for a 18" finish height with seat when I set finish. BTW, the 90 elbow for waste discharge is HDPE and you use a no hub, so don't plan or try to glue this. The ring in the rough in box I got has one depth adjustment ring not two as shown in all of the paper work. Confirm this before starting any work. I'm off 1" out of rough due to Duravit's paper work and let the wholesaler have it this afternoon. Good Luck