I enjoy fabrication. I have a "Full" machineshop. I can build pretty much anything. The big question is return on investment as far as time and cost. I have 12 hours of fab time in this and around $60 of materials. There is no way I will see a return on my time investment. But, I am in this for the hobby aspect. Pushing for MPG gains is an adult version of playing a video game and trying to beat your high score (while gaining some fuel savings in the process).
I love hypermiling because it is the one way to increase the performance of a car while reducing the fuel cost and reducing wear and tear on the car at the same time.
Matt