Butyl will be checked everywhere and I have a bunch on hand. I read the OSI description and I'll try it. I can always go back to Dicor. I have been thinking about using the Eterna bond tape on all roof fittings. I've never done this but the finished product looks awesome. I also think while I'm at it on the roof I'll replace that old bathroom fan with a nice one as well as the shower light globe on top. I don't know what it's called. I'm gonna take my time an all summer project and do it correctly. Goin to Flagler tonight to sit and have adult beverages. This forum is well versed in the RV maintenance world.