From what I have found out about this problem: Welcome to the "Ultralite, Featherlite, Alumalite, Superlite, Anythinglite" category. I have an '05 FR Grand Surveyor that I bought used and the previous owner showed me cracks at the bottom corners of the slide much the same as the photos of the original poster here. He stated that he noticed them within the first six months of owning this unit. The selling dealer told him there was nothing they could do about this as the material the units sides were made of were not repairable and the dealer had seen many of these type sides develop cracks. I talked to a local dealer who sells Jayco units and he told me basically the same thing. He did state that they had tried to repair some units that had sides made of fiberglass by making the repairs from the inside but the repairs did not last long. The problem seems to be that the some slides (mine for instance) depend on rollers which are mounted to the bottom of the opening of the cut-out of the trailer for the slide unit. When the slide moves this causes pressure to exerted to the side wall of the trailer which in turn causes pressure at the bottom corner(s). This is what causes the cracks. My unit has the fiberglass exterior walls, I have seen these exact cracks on units with what are described as "alumalite walls" also. As far as repair: I don't think there are any methods of repairs. One major drawback to making these unit to be light weight is the way they make these walls. The manufacturer basically sandwich together the interior wall, some type of insulation, and the exterior wall. These are glued together under pressure and heat which does make a strong bonded wall. But as these photos show and owners attest to, they will crack under certain strains and pressures. I put Eternabond tape over my cracks only to keep rainwater from intruding into the cracks. I drilled a 1/8" hole at the end of my cracks to prevent any further cracking/splitting then put Eternabond tape over the crack to prevent rain water from entering the cracks to prevent any further damage and so far this has worked for me. @Jim Coolyard: I don't think this problem is exclusive to any particular manufacturer or model. In my opinion it is a major design flaw and ALL the manufacturer's know this.