[The donkey CRX]

I "think" what you are seeing with your gas gauge moving slower in the top half of a tank of gas is due to the nature of how the gauge sender works. All cars I have ever owned exhibited this trait. Even the two identical Honda VX's do the same thing, except one stays on full for almost 150 miles.

I think the lip you reference would be OK as a start to an effective eco front end for your car. The lip only needs to go down far enough to be below the lowest point of all the undercar components. If you plan on doing a belly pan this would make a good transition to it.

Don't forget that blocking the air flow in to the engine compartment is also very important to improving your aero. But saying that, I would personally never block the front air intakes unless I had a good after market water temp gauge to monitor water temps.

Thanks