Hi,

The split bus wave goes like this.

Please your left hand at 12 o'clock on the steering wheel and while
keeping your hand on the wheel, lift your hand up. The gesture is
plainly visible from the oncoming vehicle.

They didn't make the windows big enough to hang your arm out of because
you really do want to keep both hands on the wheel in a split bus.

BTW, you right about the Vanagon wave being much bigger - about the
difference in size between the two vehicles.

Conrad