"New" Work, rough-in ~ pressure-balancing valve,

[TonyBagadonutz]

I am installing a pressure-balancing valve in my bath remodel ("new"). I'm a bit confused by the terms/definitions used in the install guide...a little clarification, please?

The valve is being installed on a wall that will have 1/2" rock and a 3-piece shower surround. The instructions say "thick wall" and "thin wall".
What is "thick wall" (wood lathe and plaster; rock and tile) ?
What is thin wall (rock and surround; rock and tile)?
Do I need to care?

In either case, the instructions call for a 2 3/4" - 3 1/2" distance from center line of supply/valve to finished wall surface. ...and the insturctions also call for different diameter cutout/s, depending on wall - thick = 5 9/16"; thin = 4".

What kind of wall do I have - thick or thin?
What size cutout should I make - 5 9/16" or 4" ?
Does my cutout diameter really matter - as long as I maintain the 2 3/4' - 3 1/2" dimension?

What I am looking, instructions wise, is for a Kohler K-304-K
here is the install instructions (in .pdf format):
http://www.us.kohler.com/onlinecatalog/pdf/114811_2.pdf
...On page 9

Thanks in advance.

 

[hj]

valve

A "thin' wall is the plastic wall/surface of a fiberglass unit. The smaller hole is so that the plastic "ground" device on the valve that is used to set the finished dimension will be left on the valve and the thin wall will be clamped between it and the decorative trim ring to secure the valve in place. Normally that hole would be made to the larger dimension so that the ground device would pass through the hole in the wall and set so it was even with the final wall surface.