Insurance, residual replacement value for special accessories

Hello, I have a problem with my insurance. In my car a roof avalanche hit on it, roof pressed in, damage 3920€ ! The vehicle is a “disabled” just converted vehicle (seat rail extension, seats padded off, mirrors adapted, etc. ), but runs officially as a normal car. In addition, I have much more expensive extra accessories, fixed 230volt system, preheater, voltage converter, video system, car PC, hifi system, etc.). l claim that the value of the accessory and that of the disabled person just conversion is greater than the residual value (according to Schwacke 4200€) of the actual vehicle. After all, I would have to have this included in the purchase of the vehicle, and would certainly be ~4000-500€!!! So for the new purchase this is at least about 900€! But the insurance only wants to replace the Schwacke value. A reviewer came by and got a copy of the vehicle license, took a photo and is wide My accessories didn’t interest him, I said, “It doesn’t matter when it comes to replacement. Is that right? Can the insurance just push the replacement value to save money? What should I do now?