I put that stuff on everything!! From the propane tanks shroud to the AC cover on top. I also put it on the rubber trim that covers seams. It is real good stuff. I will have to watch the video and see about the skylights. I would assume it would be just fine, as they are just plastic.
Just watched the video as mentioned...............I don't put 303 protectant on the roof material itself. Crossroads recommends nothing be used except a good cleaning at frequent intervals. But everything else that is rubber or plastic gets it.