Demounts are fairly common in Australia and over the years I've read plenty of discussions about them - the one recurring issue seems to be weight distribution. The rear axle tends to be overloaded and the front axle tends to be light, this is because the centre of gravity of the demount is behind the rear axle (especially with crew cabs) and it acts like a lever lifting the front. Even adding air assist springs does nothing to move weight off the rear axle and onto the front axle - but it makes the vehicle look level.