[Christ]

I don't think I can postulate as to the importance of them being tire-width, but I did notice those pinch-welds would also be a great place to hang an inner skirt, if you were so inclined. They appear to be just inside of the tire's inner surface, which might be close to ideal. Of course, you probably won't want drill the pinch weld, but if you could mount the inners to the original rocker cover as well, you could use the pinch point as a guide, and mount your angle right into the angle created by it. You could also put some kind of sealant on the piece before you put it on, so that water/dirt don't get up in there. Silicone would work fine for this, even if silicone doesn't adhere to the plastic very well, since it will harden and work as a gasket without falling out. For no real good reason, other than myself having been a professional caulker, make sure you slick it down good so it's not all bumpy and stuff.