I have seen a lift on the back of a class A that had a Gold Wing on, that should be comparable with your Harley, perhaps even heavier. I believe those are mounted to the frame rails. Might be worth looking into pulling your little truck behind 4 down, so there's no additional weight on the back of the coach.
By the way, I tried talking my wife into a toy hauler quite unsuccessfully. She equates it with parking the bike in her kitchen (not that there's anything wrong with that, right?)
Good luck in your quest to get away from it all, while taking it all along with you!!
2008 Rockwood 8315SS