Instead of just a simple hammer notch, make it follow the circumference of the hammer by a bit more than the amount of travel needed for a notched safety to operate. If that were cut true, it would work nicely.

I would also be sure the only place the trigger bar contacts the sear bar is near the aft end. I'm thinking too much contact along those parallel surfaces would make for somewhat erratic function, especially if any debris gets in there. The contact between those two parts could be limited to the facing of the adjustment screw if the screw was mounted inside the trigger bar itself. Access might be a bit of a problem but that could also be a blessing. You could do just a simple hole upward through the guard area to get to the screw.

A small set screw in from the side of the trigger bar to keep the adjustment screw from moving might be a good add. You will probably only adjust that trigger once but it could still be altered later if need be.

Thinking outloud.