I altered the spring using the method described by Zonie and I changed the shape of the frizzen's toe. Unfortunately I was a bit too eager grinding on the front of the toe and now I have to add about half a mm (20 thou) of material to it for the pan to close reliably. As the frizzen is hardened throughout I'm trying to decide between using soft soldering, tig brazing, or tig welding. I'm not sure which of those methods is the best.
Regarding welding. My tig setup goes down to 5 amps so I should be able to weld a small spot on that toe without annealing the rest, but I never tried to weld hardened steel and I'm expecting the weld to crack on cooling. I hread somewhere that stainless filler rod is sometimes used with hardened steel and slight preheat (slight as not to anneal the piece). Does this sound like it could work? I wouldn't mind a slight permanent discoloration this would cause.
Regarding soft soldering I think it would be a good way to test a number of different shapes quickly, but the solder may be well to soft for permanent use and I'm not sure if it'll stick to the toe without heating the whole frizzen.
Regarding brazing, it is a bit more difficult to do it on such a small scale so my first choice would be to weld.
I spent some time firing the pistol with the altered spring and toe. It definitely works better than before with regards to flint life, but I suspect there are some serious issues with this lock's geometry as it still manages to crack the flint sometimes. I tried to hold on to the cock and let it move the flint across the frizzen slowly. Doing that I discovered that flint kind of binds around the bottom edge of the frizzen and overcoming that bind rips chunks of flint out. Some posters to this thread commented the shape of the frizzen is not right around the bend and I think this may be why it is binding there.
I'm slowly getting more and more comfortable with the idea of replacing this lock with a better one, but before I do that I'll try few additional alterations. Once I add a bit of material to the toe I'll probably try to alter the shape at the bottom of the frizzen's face.