I fitted the a firestone air suspension to my MH. A fiat Ducato chassis and it made a huge difference in handling. you can also adjust the suspension according to load eg when you load up with vino on the way back from France just add a few more psi and you wouldnt feel the extra load. Also much cheaper than an extra leaf and if you are handy you can fit them yourself. The system is called DriveRite, and can be seen at www.driveriteltd.com The site also gives a list of dealers
My experince, altho' good, probably wouldn't be much use to you cos I fitted a rear airbag set on my RV due to wanting to carry a motorbike on the back. The diference was fantastic. Raised the back end by about 3" (with the m\bike on) and cornering, either loaded or unloaded was MUCH better.
Of more use to you, may be the fact that I've NEVER read a bad report about Air Ride, everything I've read on various Forums has been positive.:thumb: