GVWR is easy; GVWR shall be specified by the manufacturer as not less
than the sum of: curb weight, dealer installed options weight, occupant
Another way to look at it each manufacturer determines the maximum
acceptable weight limits for each vehicle by considering the combined
weight of the strongest weight bearing components (the axles) and the
weaker components (vehicle body, frame, suspension, and tires).
So you need to upgrade the body, frame, suspension and tires to safely
increase GVWR. Or just move some load to the trailer to reduce GVWR;
just keep it within GCWR.