I don't think that rocking the car from side to side will do anything other than give you a bit of exercise. The tanks are pretty simple with just a balance pipe between them and a vent pipe from the top of the LH tank. The LH tank will take a bit of time to level off with fuel transferred from the RH tank, waiting a few seconds between clicks will allow this to happen. I have done the rocking thing when refuelling some aircraft but they have much more to go wrong and stick, float switches, flapper valves, baffles etc. The M3W is just a pair of tanks.
