I replaced my cracked skylight this year. Winnebago no longer had these so I ordered one with the same dimensions online from EZ Tops World Wide. Old one was removed and and all traces of old sealant cleaned off, first scraped with a dull putty knife then followed up by scotchbrite and paint thinner, wiping with clean paper towel. The mounting surface looked "new" so a good foothold for new sealant. The skylight supplier specified Surebond 140 sealant. I drilled holes along the skylight flange for #10x3/4" screws, and I used new stainless ones. I dry fitted the skylight by attaching at the four corners then drilled pilot holes into the roof at each flange hole. Using the drilled holes as a line, I applied a bead of sealant around the whole thing and set the skylight in place. Started each screw, then incrementally tightened them around until sealant started squeezing out from under the flange. From there I put another bead of sealant around the edge, and sealed the heads of all the screws. Probably took 2 hours start to finish. Just for giggles I wanted to see how easily the old skylight would crack so I flexed it and it shattered into a dozen pieces. So pretty much any impact from a branch or maybe even hail would've done it in, it had no integrity left. Contrasted to a new lexan skylight which can probably take a hit from a baseball bat and bounce back. So skip the eternabond and self leveling sealer, go with what the skylight supplier recommends and not have to re-seal every year or wonder about it. I have no doubts that my skylight install will outlast the RV now.
Mark B.
Albuquerque, NM