I did the exact same thing to mine. I was told its OK to widen the fenders as long as you make it look stock again.
Scoot what group do you run with. I just want to make sure that if I do it this way I will pass tech at other ARMA tracks.
Just be sure you give those tires enough space under that fender, to "grow" under acceleration. I have seen tires gain up to 2 inches of circumference when spun hard....
In fact we talked about that today. If I do it this way we'll put 1 3/4 between the fender and tire.