Take two plates of a suitable material, and attach them at one end at a 90 degree angle, such that they form a V shaped assembly. The plates will block some of the vacuum flactuation frequencies inside the V, so a Casimir-like force will appear on the two plates. But since the plates are at an angle, I suspect that the forces should not be exactly opposite each other, and should therefore not cancel out. If this is correct, that would produce a small amount of net force, probably in the direction of the V's "mouth". I think this should be easily testable by using sound waves as a model... Have any such tests been made? Have anyone done calculations on this geometry? Any other comments/thoughts on the matter?