If you are target shooting and capping on the line there really is no need for a half cock notch.
More so if you have set triggers which is basically another lock and which would not be set in any way during capping.Fingers out of the trigger guard until the sights are on target.
I don't even think I have sufficient clearance to sneak my capper under half cocked hammer on my target rifle.
Lots of quality built percussion target rifles were made this way in the 19th century .
They must have either primed on the line as well.Or so we might hope.
I have seen the hammer blocking peg set up on old guns as Jim has shown .It also provides a visual clue like a chamber flag .
I wonder what the old rules were like at some of the old time matches.Did they have a range safety officer?
.Probably not.
Half cock is really important for a flintlock to make the cock (relatively) safe during the priming sequence
And to have it in a primed ready state while hunting.Maybe the heresy of no half cock is greater from a flinters perspective.
Regards Stuart