I heard from Scotty he's out in the jungle with a bad connection, so later...
But I sailed the 76 with both 15/12 and 16/11 the other day and both setups worked really well. If anything, the 16/11 seemed to go upwind and plane up just a bit better at the price of bit less ease in setting up the top turn. The 76 is quite "big for its size" already, so maybe the 15 front fins are there to make it initiate turn easier and the 12 rear fins to keep some drive with this shorter shape. But again, we're talking subtleties here.