OK, so I'm setting up a Mitsubishi Express 4WD camper for a trip to the
Kimberleys (via Flinders Ranges, Oodnadatta track, Alice, Katherine, and
returning down the west coast and across the Nullabor).  It has 215R15
AT tyres fitted.

http://tinyurl.com/yu4n2a

I have no idea what tyre pressures I should be using.

I have a couple of issues.

I know there should be a plaque somewhere with tyre pressures on it, but
I can't find it.  (I have looked inside the filler cap, on door pillars,
in engine bay, inside glovebox.)

I have been running around with 36 PSI all round and that seems to work.
 The steering is heavy at low speeds, but it isn't a real problem.

I had some new tyres fitted yesterday, and the tyre fitter suggested 50
PSI to make the steering lighter.  The max pressure stated on the tyre
is 44 PSI, but the tyre fitter said it would be fine.  The steering was
certainly a lot lighter at low speed, but such high pressures make me
nervous.  I was under the impression that over-inflation can lead to
uneven wear.

I've dropped them to 45 PSI and the steering is still nice and light.

The first question is, what pressures should I be using on the highway.

I have seen it suggested that I should drop my tyre pressures when
tackling corrugated roads, such as the Oodnadatta track or Tanami Rd.
One book suggests that this improves comfort, and reduces tyre and road
surface damage.  Question is, how much should I let them down?

I understand that I should further reduce pressures if driving on soft
sand.

Can anyone offer at least rough guesstimates of the range of pressures
that might be OK in these circumstances?

Ta

Moike