Adam,
According to studies by ASGCA member Bill Amick, here are average distances for the main "classes" of golfer:
Tour Pro -291 Drives, 226 Max Second
Gary Good/Pam Pro - 255 Drives, 214 Max Second
Mal Middle - 212 Drives, 185 Max Second
Sam Senior/Gail Good - 190 Drives, 149 Max Second
Maude Middle/Sally Senior - 137 Drives, 121 Max Second
The USGA did a one day study of drives on a public course in NJ and came up with similar results. Less than 1% of drives went over 260. There were little clusters of typical drives centered at just about 260(3%), 230(16%), 200(57%), and 170(20%)and about 140(3%), which was oddly symetrical.
Don't know if that was exactly the answer you your question, but that data answered mine - I have recently downsized back tees to merely buttons on my new designs/redesigns and devoted more tee space forward to the 200 yard drive and 6300 yard total course.