I've got a new GLOCK 17M MOS that I'm going to mount a Gen 2 Steiner on. Stay tuned for pics.
I have no experience with the optic cut VP9 or B&T’s plate for it. My only experience is with the optic ready M&P 2.0 and B&T’s plate for it. The M&P has round bosses in the optic pocket for mating up to the plate. B&T made the corresponding female optic pockets that meet up square in shape instead of round. If I remember correctly one of our instructors had the optic/plate combo come off while shooting. On the sample I tested, the plate came loose twice during testing and that was not at a high round count. This was after following established mounting procedures.