Air Bags, Rubber Springs are not the correct solution when installed TDC on Axle. Look at the geometry of springs they divide and distribute the weight much better then bags and rubber spring add-ons. You are much safer with adding additional leaf or over load springs. Look at the increase Body roll Air bags will produce when vehicle is NOT level.
Two years ago I and the Wife were traveling back Home form Wyoming (We spend several weeks every winter traveling the West for Snow we average 6/8K yearly in the Rockies) The road conditions on I90 at Murdo worsen to the Point I and decide we would Stay in Murdo until the roads clear Up, About 1/2 mile ahead of us was someone pulling 5th wheel toy hauler, a big gust of wind develop and blew the truck and toy hauler off the road about 4/5ft into the median ,When the truck/trailer all of a sudden tip on its side and slid into the cross over and the trailer rip the hitch form the frame and the toy hauler crushed His Daughter and son-in-law killing them instantly, I inspected the truck after the emergency was over. . Sure enough it had Air bags and one of those Bolt on (POS) B&W 5th wheel hitches. All my trailer(s) are Goose neck with custom build hitch install in all our Pulling Vehicles. . They are designed NEVER to be broken the Truck frame will have to Buckle before it will be rip off. I special order all our trailers, Sure the GNs are NOT popular and adding springs cost More $$$,but look at the price this owner Paid, Putting faith into these add-on products may nor always be the safest choice ,it In most cases is designed to be convenient NOT safe.