Keeping to the question at hand (quickly), will the gen bezel for the 42PO snap on no problem? Is there any extra pieces or rep pieces that still need to be used?
The ETA 3G and 4G cases do fit the gen bezel. They do click on but they are tight to the case. You need to use the plunger spring that came with the watch. If you use the gen click spring it will lock the bezel up. I have done 4 of these so far. Not a big number but that is my experience. 21J, 5th Gen or any other 42MM cases.... Your millage may vary.