anything that is attatched to a tow bar is classed as a trailor as you are pulling an unpowered unit. A trailor is not covered by insurance unless your policy has trailors listed but you might find there is a value limitation as owners of caravans found out years ago after an accident. As long as the vehicle has a working light board and tow vehicle registration you shouldn't attract the interest of the police. having home made mud flaps might cause more interest than what you realy want. Personally i would just leave as is and tow it. Obviously stick to the speed limit and you'd be fine. the 85% is only a recommendation for an unbraked trailor. with a braked trailor the towing weight becomes stupidly high in relation to the tow vehicle. As for no body panels that wouldn't be an issue. you can legally drive a bus on the road as just a chassis so how odd is that ?
towed the scenic back from manchester and that was classed as sorn. with all the anpr cameras on the m6 we never had any letter through the post or was stopped by the passing patrol cars.