Definitively, the anhedral stab was used to control the pitch down tendency in knife edge when the rudder hinge line was moved back to vertical.In knife edge, think about this: the fuse had a positive angle of attack. The bent stab then gave an effective "up elevator" component. Visualize it, please.The same effect can be had by moving the rudder hinge line to less than vertical. Think "Taurus" generation. That effect was for extra up elevator for spin entry, but take one of those (Taurus, Orion, Perigee, etc.) and put it in knife edge, add the rudder, and behold, it climbs to the canopy like a demon!Downside of the anhedral stab is that in a cross-wind, it would make the plane pitch up. Rudder hinge angle did not have that problem.In the desire for true neutral response to control inputs, most designers left the rudder hinge line vertical, and compromised by doing other things. Remember, in the Curare days, there was no control mixing in the Tx.Does that help to clear things up?