IMO, take the max towing capacity of your truck and subtract one ton of weight. The remaining weight is your max tow weight meaning, loaded with all the junk you will put in the camper!. With this formula you have some room for performance without dogging your truck. Yes, it is limiting but safety on the road is important. Also, any hills or grades you encounter will be easier. Camper salesman will try to talk you largest camper you truck can handle. Once you roll off the lot with it you will realize you made a mistake and need a bigger truck. Just my 2 cents, as if anyone cares!
