Toilets, Sinks, Showers, Tubs and Disposals - Installing new Delta tub/shower valve

I am installing a new single handle Delta tub/shower valve. I have ripped all the sheetrock off the wall and have removed the old valve assembly.

My question is the Delta valve body comes with a "Plaster Guard" - a plastic ring screwed to the valve body. However, the instructions are real confusing as to how to place this valve.

I will be using 1/2 green board, with 3/8 cultured marble panel attached as my finish surface. Do I install the valve body with the plastic plaster guard flush with the sheet rock, or out 3/8 to be flush with the marble?

I have called Delta help line . . . spoke with three different people . . . and go three different answers. :wall:

Any help would be appreciated.

Hi doitright,
-that Delta system has to be flush with the outermost surface. ie the marble front in your case. :cool:

Do it Right - do it once.

Thanks . . . I appreciate the response. I will install plaster guard 3/8 outside the sheetrock . . . making it flush to outside of 3/8 marble.
Lee