Hi Cuppa,
I can't help myself from responding. The reason you own a Tvan is to do these sort of trips. Solo is not an issue particularly when there are so many people crossing the Simpson. If you get stuck, people on these trips always help. Besides you would be blocking the track so they have no choice.
Reversing in deep sand is not fun, as the Tvan or anything for that matter, just wants to go the path of least resistance which usually is not where you want it to go.
My advice for what its worth is to maintain low tyre pressures on all wheels(14 to 18 depending on load, humidity and temp and 12 - 14 in the tvan/ don't speed or they will overheat) i.e. have the Tvan tyres on slightly lower pressure than the tug. This way the Tvan will float and go wherever the tug goes. Stick to a gear uphill second or third low and you will usually just drive up the dunes. Don't let off power until the tug has crested. Hesitating at this point sees many people stuck just before the crest. Also, use the sand flag and radio to avoid unwanted greetings at the crest from oncoming vehicles.
The Simpson is an outstanding trip made even better with the Tvan. I'm jealous.
Have fun.
MM