Consider the following - the pin weight is for a completely bare trailer, - no options, no propane, etc. The total carrying weight of the 31 is over 4000 pounds. Figure that the pin weight will be 20 to 25%. You will easily exceeding your unloaded pin weight if it close to your trucks capacity, just by adding fluids.

Also look at the rear axle capacity, as well as the GVWR of the truck. Adding springs and air bags does not increase the GVWR as specified. The first thing I would do is to weigh the truck as loaded for a trip. A full fuel tank, the occupants who will be traveling in the truck, any tools, blocking, etc. Add 200 bounds for the hitch. Subtracting this weight from the GVWR for the truck, and what's left will be the maximum pin weight you can carry. This will give you a good start.

The factory pin weight and dry weight can be used to calculate an estimate of what the pin weight will be when the 5er is loaded to its GVWR. Here is the process:

To determine if your truck may be able to carry a certain 5er do these calculations: For the 5er, divide factory pin weight by the Dry Weight from the factory. This will give you a number most likely between 0.15 and 0.20. Multiply this number by the GVWR of the camper. The result will be the estimated maximum pin weight your truck will need to carry when the camper is fully loaded to its GVWR. If the dry weight of your truck plus this pin weight, plus the weight of passengers, fuel, hitch and any other cargo is greater than your trucks GVWR that 5er is too heavy for your truck. This will be the best you can do until you have the camper and can weigh the rig hitched and the truck unhitched.
5er Dry Pin weight / 5er Dry weight = pin weight ratio (PWR)
PWR X GVWR = estimated pin weight of fully loaded 5er

If you have a generator and extra batteries, the pin weight of a Redwood 36xx may be in the 22-23% range with a full water tank. (Ask me how I know.)