Once read somewhere that you must have at minimum 30% of the total load at the front wheels, so if you ever weigh, calculate if it is below or above that.
With that large overhang I expect mayby even much lower then 30% on front, so it sertainly can explain the complaints you have.
Also with that large overhang , mind that things behind the rear-axle give more weight on the rear axle then the weight that is placed because of the leaver-effect, and lifts up the front.
What you can try , if weighing prooves this all, is to replace some heavy things like watertank if possible , beween the axles as much to the front as possible.
Also mind the tire-pressures, high at back and low at front
Back even higher then the maxloadpressure printed on sidewall.
TRA allows 10psi higher for LT tires and 20psi higher for truck tires.
So if the pressure yyy in "maximum load xxxx lbs AT yyy psi(cold)"is fi 80 psi then you may fill to 90 psi, and it is supported by the tire-makers, they cant sew you for it. At lower speed even more then maximum load of tire is supported by the TRA.
My advice is also to weigh , then you will be surprised of the overloading of the rear-axle and low load on front, is my prediction.