I am with everyone else....
DON'T NOTCH THE FENDER!!! You will kick yourself all the way to the road the next day! It doesn't matter if you have a 100% work tractor....you will regret it later. Just because it is a work horse doesnt' mean you can't take the time to drill the hole, I am sure you have access to a drill press to bore it out a little shorter. In order to notch the fender you need to get a sawsall in there or heaven forbid take a hammer and beat the crap out of it to bend it....
....that will be NASTY!!
Not a wise choice...the tractor didn't do anything wrong to deserve it...