As long as your trailer rides reasonably level there is no concern. If it does not, check your trailer pin weight vs the truck's rear axle capacity (GAWR) - you may be overweight. When loaded a fifth wheel is pretty heavy on the hitch and often far more than the advertised pin weight. 20% of total weight is fairly typical.
Air assist, e.g. the Firestone Ride-rite air spring system, doesn't acually increase GAWR and GVWR, but it can be used for leveling. See http://www.ride-rite.com/
Goodyear make sthem too - http://www.goodyearindustrialproducts.com/airsprings/about.html