Shape is as important as size, in my opinion. I think it's Goodmark's 4" cowl hood, that looks like a wedge, and to me doesn't look good. Rarely see that on the 2", so only a concern on the bigger ones.I think a 4" cowl can still look good depending on how the rest of the build looks, but more than that is too much. I've seen them on Camaros and Mustangs that looked rifuckindiculous.