YOu need to "Reverse Engineer" these locks when you want to tune them. What is important is Not where the full cock or half cock notch is, but where on the frizzen the edge of the flint strikes, and at what ANGLE it strikes. The best tuned locks strike the frizzen approx. 60-67% UP from the bottom of the frizzen, and will strike the frizzen at a 60 degree angle at POI. ( Edge to face)
From the picture your cock seems to want to strike the frizzen too high, and you will BE BASHING the edge at almost a 90 degree angle, Crushing the flint's edge. You don't get many strikes out of flints with a lock in this condition.
Yes, with your skills, I would look into changing the location of the half cock notch in that tumbler.
Be careful of the height of that cock screw-too. It looks like it will strike the top of the frizzen before a short flint will even contact the face of the frizzen. Shorten the height of that screw- its decorative, more than truly functional as it is.
The angle of impact is intended to take advantage of the natural fracture lines of flint, and other silicates, so that not only do you cut steel, but the edge is broken off with each strike just a little to give you a new,Sharp Edge for the next shot.
The WRONG angle causes the flint life to be shortened obscenely, and the need to constantly move the flint in the jaws to get what life it does have out of it. A royal PITA, IMHO. Along with the wrong angle, these locks are notorious for having way too much tension in the main spring at full cock. I have seen many that have 40 lbs. and more spring tension at full cock- bruising your thumb and finger tips just cocking the darn things. Heavy tension springs also contribute to shortened flint life.
And, don't ignore the need to have a frizzen that jumps open quickly when struck. The point on the frizzen spring where the cam on the bottom of the frizzen rubs must be polished smooth, and the cam shortened so that you don't have to Lower the frizzen spring to get the frizzen to open. A frizzen only does ONE job: It keeps the frizzen closed when the gun is carried muzzle DOWN.
It is Not suppose to hold the frizzen against the impact of the flint to aid in cutting sparks from the face. That seems to be one of the great misunderstandings in making the modern replica locks, particularly those made overseas.
If you can't modify the tumbler adequately to change the position of that cock at half-cock, then consider bending that cock down to get to the correct Angle of Impact. There are a variety of things that can be done with the mainspring on these locks, depending on the particular design, to reduce mainspring tension and give long life to these mainsprings. If you want to know what I think you can do, send me a PT with a picture of the backside of the lock, and I will describe what and where. :hatsoff: