Clearly the statement "Half the width, double the mileage" was not really meant to be take literally. While it will reduce drag not enough alone to double MPG . As for weigh the old rule was about 400 lbs reduction to get a 1 Mpg in fuel. That of course it not the case now but it still is a larger number.
How the engine use the fuel it has is the number one issue in a car like ELIO.
If the ELIO ever gets into production we will know if it was the right call to build a new one
You know that. I know that. Perhaps someone should let Paul know that. I've come to realize that almost nothing Paul or Elio Motors says can be taken at face value. That is just one of many of his engineering claims that is mostly sales talk with a large helping of bunk thrown in.
Sort of the point (at least to me) of this whole discussion is that if Elio had chosen to go with an existing powerplant, they would be $100-200M closer to production. By the time they are done with development at IAV, they will have dumped $50-75M or more into the engine. Instead of using existing plant equipment, they will need another $75-$150M or more for equipment to build the engine. The money that they have already spent to get a 2-minute video of the engine would more than have paid for a full fabrication shop, professional-lever car guy fabricators and 25 pre-production prototypes with existing engines, which would now already be close to fully tested.
IMO, even if Elio ever gets to production, at best they will have survived a series of poor decisions. They still talk a good story, and I don't blame any of you for hoping they will make it to production.