Actually a question. What are you calling "over cocking"?

Does the hammer just pull back (farther than where it rests cocked on the hammer notch) and then move forward onto the notch and have a normal SA let-off?

Or does the hammer move back too far and stay there giving a funky SA let-off?

It does the latter, it lets off a funky single action let off, the hammer actually goes rearward just a little farther when pulling the trigger in single action mode and then releases forward before going home to the bushing/firing position. It single action cocks past the single action stage by allowing the hammer to go completely beyond that point, the single action sear is nowhere near it's resting point, the hammer is completely free of the single action sear and is about at the point one might use to remove the hammer from the gun. The trigger sear actually sits on the bottom of the hammer, not the hammer sear. Do you think that the hammer is wrong for the model? It looks right and aligns with the bushing when in the firing position.