Installing body jets in shower

Hi,

I have a question about installing body jets in a shower. I bought some hansgrohe body jets and it says to install a test nipple to each drop-eared ell, then finish the wall (which will be tiled), then mark the nipple flush with the wall and subtract 7/16" so that the nipple will be recessed 7/16" behind the finished surface of the wall. So I have 2 questions:

1) how do you cut the nipple to that length, do I just use a hack-saw and not worry about the cut end's threads or do I use some sort of tool (a file maybe) to fix the threads at the cut end.

2) once the pipe is the proper length how do you screw the nipple to the drop-eared ell? It seems to me that I can't get a pipe wrench around the end because it is recessed into the wall.

I was thinking that I could just install everything to the correct length when I do the rough-in since I know that the backer (1/2") plus tile (3/8") width, but I'm not sure how much thickness the thin-set/kerdi sheet will add and the instructions seem to indicate that it needs to be accurate to 1/16" or do I have some wiggle room with that figure.

Thanks for your advice,

Scot

I'll do that,

Thank you