Your policy should have an appraisal clause where if you disagree you can go into appraisal. Get written appraisals for you coach from dealer first. I that doesn't work, then tell them you are getting an independent appraiser, they will do the same, then you pick an independent third party to mediate. I don't know what state you are in but I believe most state require the appraisal clause in the policy. get you agent involve, they earn a commission on you every year.
Marianne & Jerry. 2019 Forest River Berkshire 34QS
USS Decatur DDG-31 1971 to 1975
Fort Snelling Nat'l Cemetery Memorial Rifle Squad