Sorry, just seeing this. It was an automotive window urethane which was put on after the POR-15 (paints over bare steel or rust to create a shell coating to protect it. I also put on new window trim as well. I am all sealed up now!Unsure if you added more about this project, but I am in the same PNW boat and this thread is long.What caulk did you use and what was the outcome? Thanks!!