I have a question I tow a 8500 travel trailer and have a reese strait line hitch rated for 15,000 lbs spring bars. I am getting alot of tailer sway and I think I have the hitch setup right. Watching the rear suspension last time towing seems like it wants to move up and down alot. So I was searching and found alot of people are putting air bags on the new trucks because of the leafs being so long for the RIDE. Would it be better to add the Firestone air ride or have another leaf added?