[MetroMPG]

I'm always reluctant to guess, but 5-10% @ 55 mph seems reasonable based on what we've seen.

But I do wonder about the bottom angle you've got there. Are you going to have attached flow? Are you going to have sharp or radiused corners on the top-side-bottom transitions?

Wake reduction formula: haven't seen that specifically. But you could pretty much extrapolate from the studies that compare various lengths of boat tails, truncated at various points vs. full length. (Though they seem to assume attached flow on a body of rotation.)