My quick take:
- Yes, fenders help. In classes that allow fenders, almost all of the winning cars will be using them.
- That said, fenders are NOT the biggest impactor of speed. Alignment, weight distribution and wheel and axle prep are going to be more important. Homemade fenders can take a lot of time, so decide where you're going to put your efforts.
- For the Mid-Americas, your axle and wheel selection are going to be crucial. Bluntly put, if you want to be in the hunt for the top-ten, you're gonna need to run lightened wheels. Racing axles are probably non-negotiable, too. So like your time budget, also think about your money budget...i.e., you can buy Gee Fenders, but don't buy them in lieu of a set of Mid-America wheels.