Just a suggestion, try Solar Seal to bond and seal your screw holes. It is UV stable and frankly I’ve seen it bond to every surface I’ve used it on. Most recently, my south facing window was leaking water from the outside to the inside...no bueno. Few years ago I used it on my screw holes on my galvanized metal Quonset hut barn. I attached aluminum flashing to the galvanized metal. It hasn’t leaked in 4 years. And it is still slightly flexible even after 4 years. The stuff seems indestructible. It comes in a standard caulk size tube. You can order it right off amazon. I usually have enough laying around at any given time to do a project. My local salvage-reclaim store always stocks it and I pick up 3-5 tubes at a time. Shingle comes off in the winter, no problem solar seal it. Window leaks during a storm, no problem solar seal it. Got a draft around a soffit, no problem solar seal it. you get the idea, it stands up to Michigan’s brutal winters with the high humidity swings.
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