Our crossing a couple of weeks ago, we did not see another car for 4 days, it was pretty hot and in some spots, we had to hammer up the dune (East to West, steep side first) then time it just right so the back tyres would drop over the dune, then stop and figure out where the track went as the tracks were blown over with sand. Hence we fell off one with the car in to a massive sand blown hole, which did a bit of damage to the guard on the prado. We had the gear but just a lack in concentration and mistiming was enough for us to get pretty stuck, we had to get pulled out backwards up the dune.
On Knolls Track, we averaged 8km p/h, 75 kays for the day.
In peak times, I could see it would be like Burke St, and especially the French line could be done in a single car, but the guys I was with had done the crossing a few times each and they said it was rougher than they had ever seen it. The damage to the West side of the dunes done by cars with too higher tyre pressures really chewed up the track with big offset holes up the wheel tracks.
Would I go with one car, nup, I am sure a factory car could though and get lucky, or they could crash and burn.