If you have XTR calipers, do you have XTR rotors? There is normal 6-bolt, then there is Shimano centrelock... guessing you don't have Shimano rotors from the q?
sound like they will be fine, guess you bought them as a set in which case diameter should be right which is key.
Welcome to brakes that work in the wet! (until you rip through the pads and end up metal/metal, in which case they make a nice noise and work less well, but you have so much leverage available you just mash them anyway )