ExplorOz Team replied:

Paul, to travel the Simpson you require a permit and the issuers of this strongly advise travellers do not tow trailers. Having said this however, there are still those that do but they stick to the Rig Road. On a personal note, we always travel with a trailer (450kg unladden) but chose not to take it across the Simpson on our first crossing. We gave serious consideration to whether we would tow in future crossings and decided against it. Most of the dune crests on the French Line have a tight bend that would make towing really difficult in terms of negotiating a line. The other issue of course is that you will tend to chop up the track for other travellers - the corrugations left by repeated hill climbs, grinding ascents etc is not pleasant. You are quite right about a diversion track around Big Red, but this diversion takes you over another dune that is still sizeable!