Yep I have a Glock 40 MOS...
It needs the big slide, no need for heavier aftermarket springs, that big slide makes the recoil much more tolerable when you're sending 200 grain bullets downrange at well over 1,200 fps....this pistol was built to fire full power 10mm.
The G40 isn't a concealed carry gun and was never meant to be...I'm not sure why they ever tried the thin slide to start with. To me, the G40 is hunting handgun for deer, hogs, black bear and such, I also plan to use it as my camping, hiking, ATVing carry peice. I much prefer faster follow up shots than thin slide aesthetics (I think the thick slide looks better anyway).
I've been working on loads the last several days...tried Longshot powder, didn't quite get where I wanted to go with it, good powder for up to 180 grain bullets probably but I want the 200 grain bullets at no less than 1,200 fps.
Accurate #9 got me there in spades...12.6 grains under a 200 XTP gets 1,216 fps and is well within Hornady listed load data...no signs of pressure at all...I went up to 13.2 grains before I found the "Glock smiles" on the brass.