Saw this over on ADV rider.  I love this.  I saw something similar a long time ago where a guy was pulling his Ducati track bike with a Goldwing on his way to the races.  I guess if you get the balance right there’s no reason it can’t be done safely.  That’s about 1000 lbs (with rider) pulling about 400.   Be damm sure to keep those brakes serviced though.