I have a delta faucet with plaster guard. The plaster guard is a 4 inch square plastic guard that clips on the faucet valve. The instructions state that the plaster guard needs to be flush or within 3/8 with the finish wall. Does this mean I need to cut out 4 1/2 inch circle? I will be using Durock or Hardiebacker and 4x4 inch tiles over that. This faucet will be replacing an existing faucet with similar dimensions. I'm thinking I should able to put the new faucet in the same position without moving the plumbing. Also, what's the best way to cut a circle in the Hardiebacker board?