I decided to with PEX plumbing for this so that I could easily remove it when this shower would no longer be useful. The PEX was easy to install, no mess, and since all that was required was solder on crimp fittings (there’s one to the left of the cold water valve), this was the easiest part of the installation. I did have a little trouble with the 1/2″ npt threads on the plastic shower fittings, but after modifying them with a box cutter, the 1/2″ fnpt to PEX fittings went on without a problem. A pipe wrench was used to get them about 8-10 threads onto the plastic threads and they still leaked, even with the 2 wraps of ptfe tape that’s recommended.