Flint length and it's proximity to the frizzen face at half bent, is often critical. Also, when I tune a lock, I try to have the frizzen open by itself or rather under the compression of the frizzen spring, when it reaches 3/8" off the pan. This involves any one of a number of approaches including filing the frizzen's tit (very careful here) changing the angle of the tip of the top leaf of the frizzen spring, increasing the pressure of the spring, moving the cam lump either forward or rearward so that the tit goes over the top sooner or later.
Chamber's locks usually don't need anything, but occasionally I can improve the action just a little by futzing for several hours.
Great flints are about 1/4" thick for a big lock like the Virginia, flat on top and 7/8" in length, again for that lock. Flints that have a bit of a peak can sometimes be ground on a green stone slowly and carefully too remove the peak and make them flat. Don't overdo this, cause the flint will suddenly shatter. I sometimes CA a piece of pine to the top of a flint, and then grind it off to make the flint flat. I put these special flints into the shot bag that is allocated for that rifle. I like to have a bag and horn for each individual rifle or gun, complete with everything I'll need. Making up these sets is great fun.