Doesn't the Evo bumper require cutting of the crossmember/crash bar to be installed? Isn't that kind of the same thing as cutting the frame.
The lower chin is NOT a "crash bar". It's primary purpose is to provide a point for the air dam to be mounted on to. Far from being a part of the frame and on 2007-10 JK's it was barely attached with what looked like tack welds.