Positioning the water level in new tub/shower setup. Advice?
So I'm making some progress on our bathroom renovation. We tore it down to studs and began redoing pretty much everything. Everything else has been updated except what comes after the shutoff valves by the tub. Before I put the shower surround in and finish up what's left of the drywall I need to get that plumbing situation squared away. We have a single lever water control (I have no idea what the proper name is) like this gizmo here.
What I'm trying to figure out before I do any cutting is the depth I should put the unit at. It has a plastic facing that says "this part flush with finished wall" but considering I'm using a shower stall, I'm not sure if this changes anything. Or is this one of those things I should be able to (carefully and precisely) drill the hole in the shower surround for where it would go and measure the proper depth from there?
Having never done this, I just want to make sure I don't make a several hundred dollar mistake with the wrong cut.