Love the holosight. I actually don't have it co-witnessed, per se, I have the fold down BUIS and keep them down out of the way. I sometimes will shoot it with the iron sights up, holosight off, and when I shoot with the holosight, I fold down the BUIS.
On the heavy barrel Bushie, I just put a Rock River Arms 2 stage National Match trigger, and boy, what a difference that made! It is too sweet.