I am in the process of shaving the foam of my 2003 Spirit for a better ride , and yes you have to remove those hex head bolt´s. They are probably a little corroded from the inside of the fender,try and spray wd-40 on the inside of the fender also I would give the head of the bolt a few good hard hit´s with a hammer being carefull not to damage the hex.You could also purchase 3/8 drive hex socket set ie., craftsman,snapon etc.,you only get what you pay for.Good luck