Is there a rule of thumb for installing a Moen posi temp valve with no plaster guard to use as a reference for proper depth placement? I'll be installing 1/2" hardie backer and tile that will total approximately 7/8" in total combined thickness (I think) on top of framing. I was hoping someone could provide me with a measurement as to how far the front of valve housing should protrude beyond the framing. Please see attached photo.