Semi I understand this is your design but maybe the trigger design can be altered a bit to give you some advantage. How about making the end of the sear bar a hook with a mating notch on the hammer/striker? Then, instead of the sear pin you have, you can drill and tap a hole just behind the trigger that would run up to against the rear of the sear bar. Turning this set screw in or out would enable you to adjust the sear engagement. Pressure from the trigger return spring would provide the necessary upward resistance on the sear.