Can you go at the feeder leak NOT head on? If the feeder is on the dock, you could build a little rain shelter with some 2x4s and a single piece of metal roofing in a "wife approved" color.
Just thinking outside the box.
Interesting suggestion, might come down to that. One problem would be that thunderstorms are usually accompanied by high winds that would not be blocked with roof, would need complete coverage with a hole for feed to be expelled.
Even thought about putting an extra thick plastic garbage bag over the entire thing, with a hole for the feed to throw. Ugly & would be a hassle every time I need to check on feed level & mechanical operation. But I'm really getting tired of digging through the pellets after a hard rain. Will try sealant & hope that ends the drama.