I wouldn't cut em, if your curious as to how dirty it will get, ride without the front plastic on, and just go through some wet grass, and come back and let us know if you want to cut your fenders.
Now I have thought of redesigning them, but that's because I have 400ex front a arms, and the durablue 2+2 axle in the rear, making my fenders useless for mud protection.
So I might try to add heat to the front, and see if I can't pull the fenders out a little to cover the front tires a little more.
I can deal with the back, but the front throws it right in your face on turns.