Yeah I would just leave it. If it's stuff caking up, it's entirely possible that you'd go to all the trouble to modify it, and then it would still cake up and just take a little bit longer to start rubbing.

Oh I did think of one other thing you could try. Take the fender back off and spray it with PAM or some non-stick spray. I don't know how long it would last, but that should prevend stuff from sticking. You could try spray-painting the inside with high-gloss paint, which would also reduce the amount of stuff that adheres and would probably last longer.