When I look at the specs for your trailer on Keystone's web page the primary number is the 9000# GVWR. Unlike a lot of other Keystone trailers, yours has reserve load capacity in the OE axles (GAWR 4400#) and more than adequate load capacity with the OE tires, (ST235/75R15D) at 2540#. Your cargo capacity listed at 910# is going to present the real problem. There are only two factions having authority to increase your GVWR. The vehicle manufacturer or a certified modifier. The statement below is verbatim from a NHTSA document.
"The FMVSS have requirements for the manufacturer to use proper tires and rims for the gross axle weight rating (GAWR) and the gross vehicle weight rating (GVWR). The manufacturer may determine the GVWR by adding cargo capacity (if any) to the curb weight of the vehicle as manufactured. The wise consumer, before purchase, will determine if the vehicle has sufficient cargo capacity to carry the weight of water, additional equipment (such as televisions, and microwave ovens), and luggage. The manufacturer’s certification label must show the GVWR. The GVWR must not be exceeded by overloading the vehicle. There is little the government can do to assist a consumer who has purchased a vehicle that has insufficient cargo capacity for its
intended use."
Somewhere in your trailer there is a cargo label. It would be interesting to see what it has listed as cargo capacity.
FastEagle