Josh, welcome to the club. I haven't posted in a while, and just read through this discussion.
I have put all kinds of ammo through my R9s, and haven't had any problems at all, except for Hornady Critical Defense. It was having regular failures to ignite. After doing some info net research, I found that it is accused of having hard primers. I think that the R9, because of its small size, just can't produce the force necessary to consistently light hard primers. My experience anyway.
As to the 115 vs. 124 grain issue. It may be that 115 is deemed better because of hollow point expansion reasons. Heavier bullets move slower and may not reach the critical speed necessary to fully expand, possibly making the lighter 115 more effective in short barrel pistols.
But, and this is a big but, 124 grain on target is for sure much more effective than 115 in the stove pipe.
I think that in many cases, the kind of people that are drawn to Rohrbaughs, are the same type that are willing to invest the money, time, research, experimentation, etc. to have what we here passionately believe is the Perfect Undercover Pistol(pup).
I am glad to see that your persistence is paying off.