Haven't had a problem pulling our's, but what you're thinking sounds like an accident waiting to happen.

 

50% seems to be the rule of thumb before needing a brake system on your trailer. By that I mean if your pickup weighs 6000# mt then a 3000# max for trailer and cargo would be the limit. Your Ultra weighs 850lbs, 425lbs max and as far as I'm concerned thats to much. I've seen the results of bikes being pushed by a trailer when stopping in emergency situations.

 

That's a funny question but a good one and a subjective one too.

 

I just returned from a 4500 mile trip from NC to Texas pulling a motorcycle camper weighing about 450#. My camper has hydraulic disc brakes that work very well but I still prayed not to be required to make a panic stop. Pulling on level ground you hardly know it's there but on bumps, grades and turns you can feel it pulling the rear end a little. Pulling a grade gave my 103 w 255s all it wanted. The most dangerous times for me was parking lot speed maneuvers as the bike did not have enough momentum to avoid being pulled by the camper. Based on my experience I would not pull 600# especially with no trailer brakes. Good luck, hope this helps.

 

I've seen a 300+ pound guy with a 300+ pound female rider on one. God help that poor bike.

 

Are you delivering the bikes to your mountain home? Probably best to do one at a time and install brakes on the trailer with a good trailer brake controller.

I think that is too much to safely carry. Way too many variables that can occurr.