Proper shower pipe elbow distance from finished wall?

My plumber just installed new shower valve and shower pipe elbow for the head in an open wall in a complete remodel. The elbow is a typical winged model and is fastened to a backer board nailed between the studs. He put the shower arm on, but it looks wrong to me; the finished wall will be about 3 inches out from this, so the shower arm is screwed in way back in the wall. This leaves little room for it sticking out, and I am concerned that this will be difficult to replace, and if it it leaks while doing so, it will be way back in the wall, and difficult to notice until too late. What is the correct depth behind the finished wall for this? In my experience, the "socket" or threads to put the shower arm into are always just behind the tile, to the front of the backer board, and I am concerned this install is wrong. I have a chance to correct this before the wall is closed up, and I need to know what the proper method and elbow is supposed to be.

Is there one with an extension to the front, or should the backer board be moved up towards the front so the elbow is coming right to the outside edge of the backer board when it is installed? I cannot find an answer anywhere on the net.

I am in a time crunch, so any help would be greatly apprecitated!
Tom

That does seem a little deep.I would rough it just 1" to 2" from finished wall.

Shower arms with a long "wall side" are available. They are about 2" longer/

Most blocking for shower heads are flush with the back of a 2x4 stud.

That means there would be 2" in front of the blocking.
Shower arms have a long side and a short side.
The long side goes through the wall.

A leak?

I hate to sidetrack this thread, but speaking of the shower pipe: I'm installing a bathroom with shower in my basement. With the faucet pulled tight against the wall of the fiberglass shower unit, the pipe going to the shower head is not plumb. Between the faucet and the top of the pipe, it leans back (away from the shower wall) about 3/4".

I could leave it this way, which would cause the shower head pipe to be out of level, or I could cut the pipe and use a series of fittings to connect the lower out-of-plumb end with the upper end that would be held plumb. What would you do?