Yep, I have airbags. I had a offroad camper trailer trailer initially and tired old standard springs with lots of rear end sag. The CT sat higher, more for Patrol / Landcruiser's standard ride height than a standard Pajero's ride height. That meant the CT draw bar leaned down onto the Paj's towbar, exacerbating the rear end squat in a Paj with the independent rear suspension. After researching (Pajero forum and suspension suppliers) I put HD Lovell 50mm lift springs in the front (diesel engine, dual batts, alloy bar + lights, HD bash plates meant HD was required). In the rear i added SD 50 mm lift for a better unladen ride and airbags for a load and towing the CT. That worked.
Then i upgraded to a Swan OB, heavier camper with heavier draw bar. I also added stuff to the Paj - diesel gas so a 60 ltr tank in the dicky seat space, cargo barrier, draw system + fridge + slide. The additional load plus the heavier camper meant i was nose up agai, even with the airbags at 30 - 35psi. Out went the SD rear springs, in went HD. All good again.
Then I upgraded to a Expanda 16.49.1 OB. The airbags plus HD springs handled a normal load / van with the Paj reasonably level however with the additioanl stuff for a 5000km trip around outback SA (second spare, couple of fuel jerries on the roof, load of wine on the way back) the Paj was again a bit too nose up / light in steering for my liking; and i was getting sick of the bump / thump / pitch coming for the back fo the car, especially on eneven B and C roads, occassioned by so much weight on the rear axle (load and van). teh HD sprinsg and airbags are certianly stong enough, its just the physics of the pivot point being the rear axle.
After that trip i added the WDH, it levels the car out, spreads weight to all axles and makes the towing / handling / breaking that much better. Wouldn't tow a van without WDH now i have had them.
Whether i now actually need airabgs with the WDH and the HD rear springs is a different question - as i had them i may as well keep them. I only run 20 - 25 psi rather than the 30-35psi pre-WDH. That means the rear suspensions isn't as stiff as it used to be so i have a more comfortable ride, and i guess means longer life for the bags.
It also means i don't have to use as many links on the WDH chains (use 8th of 11 links, 3 loose). Having longer chains means i have sufficeint movement to allow for the WDH to stay on for tight switchback bends (like on Brown mountain between Cooma + Bega or Clydem mountain between Batemans Bay and Braidwood). I understand that's improtant when combining a WDH with an off-road hitch that has the articulation point in a different plane to the WDH bar heads and the ball / pin on the hitch head.
So, long answer, yes i have it all for historical reasons but find its all useful.
If you have standard suspension, i'd definatley recommend you add the airbags to strengthen the load carrying capaity fo the rear springs, and the WDH for safe towing at speed. Rember, when you are offroad and have the WDH disconnected, you will need the rear suspension strong enough to hold the load and van weight up in any event.
