Have always wanted to do something like this:
Probably with a Suzuki chassis with a three-cylinder motor. Then work on the aero after. Starting with a sound mechanical base allows you to concentrate on aero, which is part of the reason for going trike, right?
EDIT: This one, I think, is precisely what I want to do:
Four wheels, but narrowed rear track. You could do the rear wheel with a motorcycle swingarm instead. Should be super light.