" Even 1.5 nmpg at 12 kts is optimistic for a boat that size. But if you can live with 1 nmpg at fast cruise, that'll get you up into the range of fully planing hulls, as there are some that'll do 1 nmpg at 16 - 18 kts. 12 kts is just a tough speed to design for, as it's not enough to plane, so...