I suspect you know the answer. You know the theory behind the techniques. Now it'll take that P word you hate.
Changing gun types changes our index, our NPA. If you aren't REALLY watching the sights as the shot breaks, you'll revert to your index (the "muscle memory" piece of our grip). glocks tend to point high for most people, so it's not unreasonable to think that in comparison, the sig will point a little lower. watch those sites!
I remember when I first started shooting glocks in production... oh so many people asked whether I struggled with the grip angle and the gun naturally pointing high. I was kind of surprised, because no, I never noticed it. I drove the sites, vs relying on index. so I tried some eyes-closed dryfire draws, and sure enough, it was pointing high...
Ryan V. B. TY56060 Come shoot USPSA w Ft Wayne Area Practical Shooters: www.facebook.com/fwuspsa