Shower head arm female thread - best way to plumb

I'm installing a Kohler shower valve and head assembly (from their designer line). The shower head arm has a 1/2" female thread where most shower head arms have a male thread. I'm still in the rough in stage so I have flexibility with how it gets mounted.

Question: What fitting should I use on the 1/2" copper that supplies the shower head?

My inclination is to use a 1/2" brass elbow that is most commonly used for standard shower head mounting and a 1/2" brass nipple. My problem with this approach is that I do not know how to mount the nipple to the elbow tight enough to keep it from leaking.

All help will be greatly appreciated. Thanks in advance.

You can buy brass elbows that are SolderXMIP in hardware stores...
Then just screw the arm directly onto it...
For rough in, just make up a piece of copper with a cap on one end and an FIP on the other to put on the threaded 90 till you are ready for trim...
(remember to allow sufficient clearance around the stub-out for removal of the nipple and install of the trim arm...)I find the easiest way to do that is slip a piece of foam pipe insilation over the nipple while drywalling and tiling...
That way you end up with a nice even border on the hole...