Ben,
As straight and accurate as most of the LPGA'ers are I would guess that if one played 10 480 yd holes(kinda like their short 5s) her avg score would probably be about 4.6...say one double, 5 bogeys, 3 pars and a birdie. A legit 4 doing the same would likely make 2 doubles, 5 bogeys, 2 pars and a birdie, stroke avg of 4.8. Overall accuracy and skill around the greens completely negates any distance advantage, especially a somewhat crooked one. You could use 8500 yards and the results would only get worse for the hacker, IMO.