drwwicks,
Well Sir, you've been given a few answers here. Most are speculative. I've done close to what you're thinking of doing. One major difference. Our coach is an '04 Itasca Horizon 36GD with the C-7 330HP CAT. Yep, being a diesel, it is constructed considerably different than the intended gasser you plan on using for your endeavor.
Now, long story short, I purchased and installed, the best lift on the market. That was the "Hydralift". I didn't do the "receiver" style mounting. To me, that's way too much play and, extra movement, not needed in this critical need of close tolerances. I removed the factory hitch and utilized the mounting holes for the steel that adapted to the Hydralift.
Now, as has been stated by one or two so far, it's not just the added weight of both the lift and, the bike but, it's the ACTUAL WEIGHT that is incurred due to the "CANTELEVER" effect by having that much weight, so far BEHIND the rear axle.
You see, our '08 Honda GL 1800 tips the scales right at, 900 lbs. And, the Hydralift, hovers between 350-375 lbs. Well, using advance math, that's close to 1300 lbs. But, when we weighed the coach, with the bike and lift on board, at a certified scale, that rear axle displayed, " 20,100 lbs." Now, my rear GAWR is, 17,500 lbs. So, that meant I was over by 2,600 lbs.
No body died, the earth did not spin out of its orbit, the sun is still shining. The coach handled flawlessly with that bike on the back for over 8,000 miles. The ride height sensors picked up on the additional weight and, compensated for it. The coach road the EXACT SAME HEIGHT with that bike and lift on there, as it did without any of it on there.
But, again, it's a diesel rig, as opposed to your intended gasser. Without a doubt, due to the construction, light weight front end, INTENDED SHORTER WHEEL BASE, adding that much weight as a cantilever will cause some pretty stout issues.
Might I make a suggestion. You CAN purchase that smaller gas rig you'd like to have. And, you CAN take your HARLEY with you AND a toad. I'd look into a SMART FOR TWO car. It's only 1,600 lbs. And a small, aluminum trailer will handle both the Harley, sitting cross ways, across the front. And, the Smart car, sitting on it normally. The Harley, probably close to my Wing, at or near, 900 lbs, the Smart, tipping in at 1,600, and the trailer, close to 1,200 lbs. That totals, 3,700, plus or minus, depending on the exact aluminum trailer picked for the job.
Now, you're way lower than your limit for your intended coach, have your Harley, and a toad for those rainy days. The only thing you'd have to worry about is, what to do with the trailer when arriving at certain campgrounds etc. Good luck.
Scott