Airbag spring helpers - any experiences?

[drive it ...]

I've got LWB prado with about 3" lift springs that are very soft. So excellent flex when running empty but trouble starts when I jam 5 people plus climbing gear on board - back end sags out badly and its a pig on the road.
I'm using Rancho adjustables, winding up makes things a bit better but really the springs are overwhelmed by full load.
Not really keen on replacing with heavier springs.
Looking at poly air bags that sit inside the springs.
Found 1 bloke who tried them, said even with no pressure they stiffened things up too much so he pulled them out. Any one in ORE land use these - comments, thoughts?

[amboguy]

What about these as a alternative to polybags? don't have the problem of puncturing a bag.

http://www.waikato4x4.co.nz/Products/Sumo-Springs

[oldblue]

I used them on a SWB Prado, Make sure the airbag inlet tube is at the bottom, they fit better that way.