Trouble with pinball simulation - pinball passes through flippers.

I'm having an issue with the flippers on a pinball project I'm prototyping. The ball reacts with all the walls satisfactorily but the flippers do almost nothing. Can anyone tell me what I'm doing wrong here? Both the ball and the flippers have rigidbodies and colliders, and collision detection for both is set to continuous speculative. The flippers themselves are children of a parent empty object at their far ends in order to "flip" correctly.