Best thing to do would be get a crown vic or something, chop the top, put a 4 banger in it with a stick, lower it, put itty bitty wheels with low rolling resistance tires, strip the interior down to just a single seat.

Easy 100%+ increase in fuel economy but why go through all that work to win a contest with no price? Hypermiling is more about being thrifty and having fun in the process (if you ask me).