OP you will exceed your payload limits on anything much larger then a 25' camper. It is difficult to understand, but your payload includes extra humans, gas, fluids, any cargo you have, and tongue weight of your trailer. You are also limited by the weight over each axle, which further complicates the issue. Payload is typically what limitation you will deal with, not "towing capacity".
We have a rockford roo 19ft which claims to have a dry weight of 3885lbs, 1550lbs cargo, and 434lbs hitch weight (dry). When I weight the camper loaded up it was right around 5200lbs. We have two kids 6/4 and a 55lb yellow lab, canoe on top, and firewood in the back. I am right at the limit, and that is which C rated tires. I would never think about towing with P-rated tires, and my next set will probably be D-rated just to be safe. That is about as big of a camper as I would ever want to pull, and I don't know that I would ever consider the GX470 to be a long term solution if you plan on pulling long distances often.
