I plumbed my shower with PEX Expansion fittings.
I also used Uphonor PEX Expansion Drop-Ear Elbows for the Shower Outlet and Handshower Outlets.
My tile guy requested the drop-ear elbows sit out far enough that the Kerdi-Schluter Membrane Gasket would surround the NPT fitting. Thus, if either of the shower fittings leaked, they would do so within the waterproof barrier. This is Schluter's approved install method. So my tile guy is correct.
However, with the proper depth of the Drop-Ear 90s set, the PEX expansion ring interferes with the flush mounting of the drywall backer board for the Kerdi membrane. It doesn't matter if it were greenboard or hardibacker or cement board, these fittings set at the proper depth would interfer with the flushness of the backer board.
This doesn't appear to be some sort of hack on my part. Uphonor makes Expansion Fitting Drop-Ear elbows, and the local supply house sells plenty of them.
Should the drywall just be trimmed a bit to allow for the backer board to sit flush, and just cover the area with the membrane and deal with the small "soft spot" in that location?
Or should I push the drop-ear elbows further back into the wall and merely use pipe nipples to make the connection with the shower arm or hand shower elbows?