[justpassntime]

I think you may be right about seeing a difference without a trip computer. Then again it may be tough even then. My car is pre OBD, so have to wait for the guys doing the MPGuino.

I need to add a support of some kind to keep it from waving in the breeze. Thinking one in the middle would do it. Found an LED light strip (very small) if I want to add a higher third brake light.

Another question...

Do the taillights on the Caddys that were the the long narrow verticle lights help with aero? The reason I ask is they extended beyond the trunk area.

Concrete,

I think you are on the right track with the extension just not the right angle.