this is what i have, and it works realy well so far. i have the load leveler kit but i was advised not to use it as i have air bags. i am not a mechanic but as far as towing goes, and i am towing massive, with huge towball weight it is working well!
http://i947.photobucket.com/albums/ad316/jaykjims/P1000036.jpg
I'm a little concerned about your rig, if it's massive - you're using inertia brakes, not electric - they're really unsuitable for anything over 1,000kg - although technically the law permits inertia or "override" brakes on trailers up to 2,000kg, they strongly recommend electric on at least one axle and for over 2,000kg it's law to have independent electric brakes on ALL wheels.
Our 1.8T has double axles with electric brakes on all four wheels and the handbrake operates the two front wheels. At about 6.5A per wheel, we carry up to 26A on the electrical cabling to the wheels, which means we're using some heavy cabling in the vehicle - 6 sq.mm is highly recommended. We start with a 30A thermal-resettable fuse just a few cm from the battery, run this into the cabin where the brake controller sits, then out to the rear and through a 12-pin flat connector (the top 7 pins are the standard flat trailer plug, so I don't need an adapter for a small trailer). This is the method I would recommend for anyone towing a considerable amount of weight. Our old van (1977 York, 16' and 960Kg) had inertia brakes and it was a pig, I couldn't stand how they worked even when adjusted as best as I could.
Your load leveler won't make a different to your air bags. The air bags form part of the vehicle's suspension, stiffening the rear and raising it upwards to allow the vehicle to maintain its height with the increased load.
Load levelers perform a different function, although the result may appear to be similar.
When you place a heavy weight behind the rear axle, the rear axle becomes a pivot (like the centre of a see-saw) and the heavy load pressing down causes a measurable (and we can calculate it too, given all the numbers) lift of the FRONT wheels. This causes reduced steering control and changes the dynamics of the vehicle on the road. Stiffening the rear suspension only makes the pivot more effective.
Load levelers actually apply a torque to the hitch (which is why it needs to have the correct, sturdy mounting like you see
here). This torque not only raises the rear of the vehicle but transfers the load upwards and settles the front wheels back on the ground, returning steering and braking control to normal.
It is therefore perfectly reasonable to use both load levelers and air bags in conjunction with each other - although I won't use air bags myself, because of the single point of contact that may cause chassis issues. I am using Load Plus helper springs, which are noisy and harsh but they give the tail more of a lift and do it through the normal suspension mounting points.
For everyone: I strongly recommend getting your hands on a video from Hayman Reese on how to set up the load leveler. It not only explains it better than I have just done by using pictures, it shows you how to PROPERLY set up the leveler system. You don't just throw it on and say it's done, you have to take measurements and adjust the hitch properly.
I have this video - I'll see if I can't turn it into a flash video.
