Drop Elbow for shower bar rough in

I am curious about roughing in a drop elbow for a sliding shower bar. Do you rough in the drop elbow flush with the face of the studs or is the depth not that critical? There will be backerboard and tile going on infront of the drop elbow, and then a drop elbow trim piece and nipple going into the drop elbow.

Thx

Depth is dependent on how much room the fixture allows. You can buy or have made nipples to any length, from a minimum value (which I don't know) to pretty long. If the fixture's socket is flush with the back of the fixture, then the drop elbow may have to be deeper in the wall than even with the face of the studs. Doesn't your fixture come with installation instructions?

There aren't any demensions for the depth of the drop elbow, here some specs of what I am talking about http://www.moen.com/shared/pdf/270sp.pdf

thx for your time

I called Moen customer service (800-BUY-MOEN, 800-289-6636) and got some help. Their advice is to make the end of the nipple flush with the finish wall. So, I would buy the shortest brass nipple I could find, screw it into the drop ell (I'm assuming this is brass) (may as well make this permanent -- use Teflon tape and pipe dope), and then mount the thing so that the end of the nipple will be flush with the finished wall. Then wrap the exposed end of the nipple with Teflon tape, add a loosely-fitted (so as not to disturb the tape) cap, and build your wall. Remove the cap, glop some pipe dope on the female threads of the Moen drop ell, and screw it on. It's supposed to tighten just as the flange comes up to the wall.

Good luck...

wow that is above and beyond, thx alot for the info