We used to run lexan diffusers religiously with the F103. Tamiya's diffuser was really nice. It helps with rear down force and stability with its strakes. Most importantly, it shielded the spur gear from rocks Some drivers even left the points on the strakes (spill plates) sharp so that if another driver plows them, they might get their tires cut up haha evil. Personally, I always rounded my corners off...I don't like pointy things jabbing me when I work on the car.