I have a 2007 Pilgrim 39' 5th wheel (So there is no manufacturer to refer to nor any warranty to worry about) that comes in at 14.5K GVWR. I normally leave this camper at my site which is about 250 m...
With a 14.5k fiver with 22% pin weight you will be averaging 5,655# per axle. With good axle equalization, the differential between front and rear axle weight will be less than you might think. If you have 7k axles and 4,000#+ capacity Sailuns, I would say go for it. You mentioned it tows great which takes care of other concerns.