The one issue that gravity racers have (at least on the track in question) is that they need to be incredibly stable. The gradient is 18% for the final drop and sidewinds are not uncommon, as well as a less than perfectly even road surface. Looking at the eco racers, you'd have a job on getting anyone to drive them as they look as if they could fall over
If the body needs to be an "elongated egg" shape, i think outboard wheels (the wheels used are only small) are unavoidable.
I'm unlikely to ever have access to a wind tunnel, and even getting some CFD is going to be a bit of a leap, so in my case it's really going top be a case of "broad stroke" improvement. If the elongated egg shape (on paper at least) is a good improvement on what's gone before, then it would make sense for me at least to try that. As far as the construction of the body goes, at least its a fairly "uniform" shape, that shouldn't be too hard to make.
What do you think?
For reference, you can see Fast Donnie Schoettler's 99mph run here: https://www.youtube.com/watch?v=CeZTOi-yAUM