Sounds like the hitch is the limiting factor here, based on your last post. Keep in mind, it was likely specified by the engineers based on a myriad of factors, GCVW being only one
. Another would be the rear frame structure, as example. I would not be comfortible simply 'upgrading' the hitch to a higher rated one.
Something else, that's not been mentioned, performance. More weight, less performance. I always councel "trying" to stay 20% below rated weights whether we're talking towing a trailer or driving a MH (can be a challenge). Your equipment will last longer and your performance will be much better, as will your fuel economy.
My humble opinion: You're asking for trouble trying to pull 5400lbs.