I have another post on here regarding the disintegration of my shaft log, the cause of which remains a mystery to several mechanics and the boat yard. The work for fiberglass repair, shaft log alignment, etc etc will be several thousand dollars. Beings no one can figure out the cause, the Progressive adjuster is dragging his feet on coverage.
Anyone have any suggestions on how to bolster my case?
Sorry to be unhelpful, but it sounds like a tough case if you don't know the cause. Insurance covers accidental damage and acts of god; not so much mechanical failures. This feels more like when my car's head gasket failed ($1000s, not covered) than when a winter storm knocked over another boat and damaged mine.
Alas, boat ownership is an expensive luxury. Sometimes it just costs a lot of money, even (maybe especially) if the purchase price was low. As my dad says, it's only the entry fee...
All that said, please accept my sympathies. I've been following your other post. Watching the dream turn into big bills, big projects, and/or lost sailing time is hard. I've been there myself and feel your pain. But you'll get through it one way or another and it will be worth it!