The rain-fly on my SD lightyear started peeling they way yours has. I simply used the old rain-fly as a pattern for a new silnylon fly. I used the old clips and reinforcements on the new fly. The new fly worked quite well and the silnylon took about 10 oz off of the original weight. And, I think making the new fly was easier than would have been the job of removing all of the old polyurethane coating.