I feel stupid asking this question but my brain hurts trying to figure it out. I'm installing a new shower base/cubicle/mixer valve but can't find any obvious means of getting the valve assembly securely fixed to the shower wall (similar to a Grohe Grohtherm 2000 exposed mixer valve - only a cheaper version). There are no backnuts or anything with the mixer valve just the 3/4 to 1/2 reducers and the shiny chrome cover roses to hide the holes through the shower wall. Help! [/quote]