You should be just fine. The toy haulers are "balanced" according to the rated weight of the garage area. Sitting with an empty garage they have some serious hitch weight...loading the garage balances it out. You'r also 1800 pounds under the limit...so no worries. Put them where they belong and tie them in good.
We where camping last year and I helped a guy guide out a Chevy Blazer from the back of his! ....he was around 800 over the limit and said it towed fine...with just a little extra sway...although I wouldn't go that far. The axels on your rig and everyone elses are set to balance the load with just the proper tongue/hitch weight. They take into account water and sewer tanks, garages, storage compartments and all that. Load it and see how it feels...move things if needed.
-Todd and Sherri
-2006 F250 Super Duty King ranch Diesel
-2012 Windjammer 3008w
-Equilzer 1200lb hitch