I really wouldn't see any trouble with the VTX being towed by it except you rear tire is going to wear almost like you were riding it!
I have a 4X8 metal trailer with a wheel chock. Works great. I'm not sure about towing the bike due to not missing things in the middle of the road. Rubber Alligators! Just mu 2 cents.
I had a friend in the 1960's drill a hole in the ball the size of the front axle pull the front tire put it in the trunk put the axle through the ball and towed it to Calif....
it just looks like trouble waiting to happen. its a good idea for someones bike other than mine.