With regards to powder selection, I'm not sure why we're not seeing more about IMR 7625 here. If I recall correctly, Henning recommends this as a possibility, but also virtually everyone that I know shooting 9mm major in SV's and STI's are using this now. I recall that for years it was Todd Jarrett's choice for .38 super as well.
With 124/125gr bullets, you can only go a bit longer in a 9x19 case. This still helps, but they are also making major with JHP's using standard Small Pistol Primers (not the SP Magnum or Smal Rifle primer we were all using back in the day). Even using these much softer primers they are only seeing very mild flattening; pressures look great.
I also observe that so many different powders feel so very different. In Open-class, comped pistols I find that to my hands, the VV N350 is my favorite for .40 and is a close second behind 7625 for 9mm. I believe that 7625 hands down offers the finest balance between very flat shooting (the ability to work the ports and/or comp) and very soft shooting in 9mm major rounds.
Way back I used HS7 (Winchester 571) mostly, though I tried HS6 (Win 540), Power Pistol, the old Action Pistol, and many others...everything except 7625. At that time a compressed-charge of the HS7(571) behind a 115gr worked best for me because it shot so flat, pressures were hot but acceptable, but it was a hard, slamming recoil...the same kind I felt from VV-3N37 only worse. It broke a lot of slide-stop pins.
Working with a friend's old 9x21 small frame Gold Team (with plain-Jane, old-school, 90's EAA 3-chamber comp), somehow the smaller charge of much faster 7625 behind a 124gr shoots just as flat, feels a great deal softer, and the pressures are lower as well. I wish that I had tried this way back when...
Oh, can't shoot 115gr in USPSA/IPSC anymore, so your other problem has soved itself. I hope that this helps someone.