I'm pretty new to flint locks too but am learning. My experience with Fuller "humpback" and ridiculously thick flints turned me to making my own from local chert which work very well. I read a lot on lock tuning, angles, frizzen hardness, spring balance, cock jaw angle, and so on and I think Hanshi summed it up the best.
Regarding Kibler's Ketland style lock, I knap flints from thinner blades and shim them both up and more up in the back with cow hide leathers shaved to a wedge shape so the angle to the frizzen is more oblique yet the flint edge still comes to rest aimed at the center of the pan and as close to the pan as possible. I almost think the frizzen face needs to be tilted back 2-3⁰ more but I'm not going to mess with it. I got 110 shots with no klatches out of the last amber chert flint before I changed it and only think I sharpened it with pressure flaking twice and that was only to get rid of burnished shiny spots on the edge that develop and stall the self-knapping action of a good lock.
I've been at war with an L&R Queen Anne lefty lock that I bought for my trade gun plank build. After detailing, filing, getting the bind out of the tumbler, polishing, reshaping and re-hardening/tempering the frizzen spring so it actually touched the frizzen toe, I got it sparking ok but not great and it would eat a black English flint to the point of not sparking at all in 8-12 strikes. I finally discovered that tue frizzen face was too soft and the flint edge was biting in and ripping off just like going at it at right angles with a file. After bending the cock down slightly so it would throw sparks into the pan instead of under the pan cover and hardening the frizzen twice I got it functional and flints last about 25-30 strikes before needing sharpened. Still, at best the sparks are dull orange and it won't spark with a dull flint at all. The mainspring is too weak to self-sharpen the edge. I think there's an important balance between mainspring strength, length of the hammer arc (impact velocity and inertia) and frizzen temper that determine spark quality and flint life. Still learning what it is and there is probably more than one ideal combination. I ended up having to leave the frizzen face as hard as I could make it with a cool water quench after heating in a rich OA flame until a magnet wouldn't stick. I only annealed the toe and pan cover to the base of the frizzen to cobalt blue to keep it from snapping and heat-sunk the frizzen the second time with a wet rag packing to prevent any anneal whatsoever. I bought a spare frizzen in case I screwed it up beyond repair and I think my next move will be to put a 1095 shoe on it. I was going to make a stronger main spring but I don't think the sear and tumbler notches will withstand the added stress for long. Anyway, it's far better than it was out of the box and I can live with it for now but will never buy another L&R lock.
My Kibler Woodsrunner lock is a beast and likes 7/8 x1" flints bevel up. I ditched the tiny, bevel-down flint it came with because it was hitting at almost 90⁰ and bouncing/skipping on the frizzen and digging a groove at the point of initial contact. I dry fired it about 30 times with one of my chert flints that seemed to do all the right things and it showed no signs of getting dull or losing the white-hot spark shower, but it definitely got shorter. It throws flint chips all over the place and auto-knaps extremely well.
My Willy Cochran lock takes 3/4" square flints, bevel up or down, doesn't matter, and it sparks very hot and well and flints go 50-75 shots with a few maintenance touch-ups along the way. Having less length tolerance than my other locks, it runs out of flint length before the edge is too blunt to resharpen and won't hold the flint well if shimmed forward in the jaws any amount. The frizzen is hard as coffin nails and skates a 60 RC test file. It also, like Kibler's locks, has VERY powerful cock and frizzen springs.
Many people with more experience than I have life left to gain often say that very strong springs aren't needed and that a lock should spark well with the frizzen spring removed. I get that removing the frizzen spring tests that the flint, cock, and frizzen geometry is correct and slicing/riding the frizzen face efficiently, but it's a sure way to bust a flint when the frizzen bounces back and slams closed on it. I'm sure there's a good functional balance to be had with softer springs, good geometry, and a certain temper to the frizzen face, but so far MY experience with only the above mentioned locks is that STRONG and BALANCED springs, a slicing flint angle, and a very hard frizzen with a lot of carbon in it makes reliable, white-hot sparks, doesn't have to have the flint pampered and coddled every few shots (other than wiping everything clean and dry after every shot in humid weather), and provides acceptable (to me, anyway) flint life.
As for the flint only scraping the lower 50% or so of the frizzen face, my newbie attitude is if it sparks well and flints last, run with it. When I manage to wear out the bottom half of the frizzen I will congratulate myself for a life well lived and a gun well enjoyed, dress it back on a belt sander, glue a shoe on it, and try to wear it out again.
