Heavy Duty is another one that means different things to different people. Mate of mine manages an ARB and he says he gets that a lot when they actually mean one that is better than standard and the heavy comes from thinking you need heavy to 'lift' it.
Bit like with cops. Often you would get a call saying there has been a 'robbery' when its a 'burglary'. Two different things with vastly different response times
- A robbery being the bloke with the mask, the gun and the $$$$ bag.....
To the original poster - I use airbags on my playdo and love them. Standard ride for around town empty, but when we tow I pump them up and away we go.
BUT.................
I agree with other posters that a good suspension setup may help you.
I actually did both and am very happy with the end result.
NOW----------------moving onto Dazzlers last comment and apologising for the hi-jack!!!!

Semantics can be a tricky thing.
For instance some married men refer to the "cheese and kisses" "boss" "her indoors" SWMBO" "the lady" "my missus" "wife", but we all know they all mean exactly the same thing.
Basically "you're screwed, just do what you're told and everybody gets to breathe!!!"
Back in my box........
Brian