Anything that can leak, will leak. Why not? It's what water wants it to do! We're busy now filling up the last of something like 60-80 holes, including various doors and vents, windows
, doorway, and now belly band. Every time we dig in to fix something, new holes and problems show up...and our trailer is completely gutted. Well, apparently not. Belly wood is still in...POs (that's Previous Owners, not POS)...(ha.) didn't think much about putting screws through the outer fiberglass! Want something attached? Screw it on (butyl rubber? What's THAT?) Then if (when) it leaked, just smear a huge blob of silicome on it!
By the say...DonnaD and many others have a LOT to say about silicone...you might consider reading up on it now, before you're tempted to try some.
As Paul said just today, while prying, sanding, peeling, scraping, and chemically trying to clean up the belly band aluminum, "Silicone is NOT your trailer's friend!"
Best...a big job for you! The satisfaction should be wonderful as you complete it...someday I hope I can feel that!