I don't know the length of his driver, but Rory's not a tall guy. I wouldn't be surprised if it was standard length.
I'm going down to a 43.50 with a 7.5* head for my 'gamer' driver. Hitting my niece's 42 inch driver w/ 12* head influenced me to go back to a shorter driver. I was carrying her driver 260 right on the button each time.