I am building a tile shower. My problem is when the plumber installed the shower faucet, which is a single round hot and cold one, it sticks out an inch or so farther than the cement board. I do not think it can be installed much farther back cause it's touching the wall in the back of it. I thought of double cement board the wall but then it will stick out an inch or so from the wall and not match on top. Any ideas?