<span style="font-family: Comic Sans MS">there are many other brands of motor mounts that don't have any kind of bracing like that at all. it shouldn't have any adverse effects on it at all if you cut it. just make sure thatyou round everything offand there are no sharp corners where cracks could begin from stress. or if you're weary about it, pick out a different motor mount. but it shouldn't be a problem. i've shaved them down before and haven't even broken one ina not so nice landing or when the plane goes into a curb or something.</span>