Sorry to hear about your hail damage!
Sounds like they are doing the low ball number on you. I have no idea why Ace would estimate your trailer so low. BTW, he has a 29 ft 1975 on the website right now for $9,500. That is the asking price and does not represent the retail value, but I am sure a 1983 would go for more. Have you agreed to these terms? You can always reject the settlement and get another estimate. I had this happen with some roof damage (wind) to my house. The original adjuster was ready to cut me a check for $180. I hired an independent contractor to work "for me". In the end I had over $4,000 worth of repairs done at no cost to me. I would suggest contacting several other Airstream dealers and see what they say. When you insured your trailer, did the company set a value at that time? I was very specific with my trailer just because of these kind of issues. Good luck to you...
Wally Byam Airstream Club 7513