Schoolbus aeromod potential?

[stillsearching]

What kind of mileage differences can be had by whaletailing everything? Could they still work on bricks? :P

I'm wanting to possibly use a used schoolbus for utility type hauling in the future... the mileage on them is actually "pretty good" (up to 12mpg with the cummins 6bt's) compared to common RV's (typically 8mpg or less) because they tend to be shorter but seeing that flat rear end makes me wonder how much mileage is being lost by that alone. The same issues MIGHT apply to boxy trailers like on a semi except that they are usually already at legal length limits, busses I think can go up to 45ft long and most are not at the absolute limit yet. I'm wondering whether I could get things up to 15mpg at 55mph or even 17mpg. (since these match what poorer pickups i've driven with toppers actually see)

[mcrews]

I posted some picks of fold out panels on the tails of 45ft trailers under aerodynamics