I have 70,000 miles experience with trailers pulled by solo bike----my opinion, with solo bike, very dangerous at best----scooter maybe even worse----for SilverWing best hitch should be frame mounted, I think ball going up and down with rear wheel not really good idea---try emergency braking....and rear wheel forced. off the ground. I think somebody in Canada made Frame mounted hitch for SilverWing.
Scooter think about strain on driveline, brakes, too.