KAT,
I talked to Welder Guy about the lip. He didn't feel that it added any strength to the device. He basically included it since it's there on all of the aftermarket ones he's seen & decided to err on the side of caution. If you need to trim the collar (lip) to get the skid to fit, it won't hurt anything.
Of course the superbumper needs that lip there to function as intended.
Tom