What's the methodology for the X-prize testing? Is it just - throw it on a dyno, then multiply by a scalar correction factor? (which I believe is how the EPA does it - or maybe did it)...
If that's the case - focus only on mechanical, not aero. Yes, I know aero is just as important - but that's not how one wins a competition as this
And you know, if the above scenario is the case - the big players will do just this (and might have a cool looking exterior)...