Update and problem solving
Well the lifting roof has proved itself. Been out in a variety of weather and its been light and airy with the sides open in the summer, and survived a reasonably stiff gale one night in the early spring. It's not leaked either, neither when elevated, nor when down and driving into serious amounts of Scottish rain.
The only real problem has been the suspension. The AirLift bags I chose to allow variation in ride dependent on load I was carrying have been excellent - perfect for the job I need them to do. But. But due to a design defect (which AirLift are aware of and working on a fix for) the top rubber retainers that fit inside the upper portion of the rear coil are able to migrate up and distort sufficiently to come through the hole in the spring hanger. Under extreme load they could conceivably pop right through (although I've not had this happen) or rotate, in either case most likely destroying the airline and releasing the pressure.
It could prove awkward to say the least if cornering under load without realizing your rear suspension was not as you expected. The supplier informed me that AirLift are working on a fix but had no idea when this might appear. So I decided to make my own. SO this might help anyone who is faced with a similar problem.
This is the problem - the rubber plug gets pushed up out of the hole in the top of the spring hanger.
I cut the top shoulders off the rubber plug to leave a square (only square because I was going to try a different method to solve the problem but realized it would not work).
Got a pair of the metal top spring retainers for the helper springs (110/130 flavour) Land Rover Genuine Part No RRC3352.
These are good because they have the locating lugs on the upside to fit into the hole above the spring.
Then a cheap 86mm diameter holesaw to drop a slot into the top of the rubber plug - this is to accept the flanged edge of the spring retainer.
Once the slot was deep enough I used a Bosch oscillating tool to trim off some of the rubber to accommodate the rolled edge of the flange of the spring plate and allow it to sit almost flat on the rubber plug. I realized when I was doing this that the oscillating tool would most likely have done the job of the holesaw although not as neatly, and saved £8.
Then fitted this combination into the top of the main coil and held it in place while I fastened on the AirLift bags air hose and refitted all the bits. A combination of lifting the axle and raising/lowering the body had it seated first time each side, with the locating tabs keeping the metal plate central.
I think the original design of the rubber plugs is intended to fit a bit higher but I kept them lower in the space to ensure that when the axle is articulated a lot the air bags will hold the plug and metal plate up tightly. I'll see how it fares over the summer - my only concern is the lack of any fastening for the metal plate- - in its 'proper' role as a helper spring retainer it is under pressure ALL the time because of the extra length the helper springs are compared to the main springs. Possibly a hole drilled in the metal plate and a hook over the top of the spring might be enough - will consider options if it turns out they're needed.
SO there you go - a fix of sorts for a problem that AirLift are still working on - theirs might be more elegant - but at least mine is at the test pilot stage!