I just plumbed a Moentrol 3570 rough-in valve. The instructions say to mount the valve so that the plaster guard will be at the face of the finished wall. Since the finished wall will be board plus tile and thinset, I'm guessing the thickness to be at 1 1/8. If I mount the valve body accordingly, what happens if I'm off by 1/8 or so? Is there any wiggle room as to the depth?