This is not really a fix. Its basically like trying to fix death wobble with a steering stabilizer. By putting the rubber isolator between the two parts that are making contact, its making it so you cant hear it but guaranteed its still hitting and in time it will dent your tub up. I don't think the rubber will ever get so loose it will fall out but the main thing is, it will eliminate the sound. You can get longer bolts and washers and space the body up, this would technically be a fix or just beat it with a hammer and rock on. Make sure you space up the entire tub, not just the back.
/\ read and know this too. All its doing is keeping you from hearing it. I think I have the mud flap at the office I cut up for this too so don't go buying any rubber floor mats or mud flaps yet.