I am losing the tub and gaining a larger 2 head shower. I have the original 2" shower line. 1.5" tub line both venting to same vent. I know I need to use the 2" line but would love to have the drain in the middle of the 4'x7' space. I know I will cap the 1.5" drain but what is the best option for the shower line. I would like to do this to code and think I can only have 3.5' from the p trap to the drain. I think I can only have 1 90 as well. Do I go the route of trying to tie into the stack directly and cut the slab from the center to the slab wall. Am I going to find that the stack is incased in the wall? Will try to attached a picture.Are there any other options.