Ive always wondered that, the leverage is almost all wrong.

Roger did mention to me that the lid on WBC flexes quite a bit when it is flipping, it was that flexion that gave it the flick that tossed 100Kg of robot from the middle of the arena against the outer curtain last tie it appeared. That might allow something of a change of flipper geometry, so that the ram is angled more out of the same plane as the lid hinge axis.

Of course, this is pure speculation. It may just be that appearances are deceptive and the ram is angled sufficiently upwards to allow it to lift a robot once full gas pressure has been achieved.