I had a crack in the fiberglass at the top rear corner of my bedroom slide. I got a fiberglass repair kit, did the repair, and used touch-up paint from Auto Zone. Very soon the crack was back. I put white duct tape over it for a while.
About 6 months later, I developed a MAJOR crack at the bottom front of the same bedroom slide, from the slide corner to the curve in the pinbox overhang. I took the trailer to an independent RV body and paint service in Fontana, Ca. I had already had the Heartland factory front pinbox frame area upgrading done. The paint and body service eventually found that the structural aluminum tubing framing and aluminum heavy sheet siding itself had cracked. They eventually welded the cracks closed, and welded in a thin steel plate (thin, so it wouldn't show under the fiberglass) bridging the cracks. Welding the steel to aluminum is a dicey proposition, with steel melting at 3000 degrees and aluminum melting at 1500 degrees. I am sorry to say that the crack is back (but smaller in width in the fiberglass). I plan to go back to the paint and body place this spring for a re-repair.
I just checked the slide, and the top rear bedroom slide fiberglass crack is back, too, although the old crack was more diagonal, and today's crack is more vertical.
