SD, you raise a good point. I usually have my flints flipped the other way (bevel side down). The flint in the pic is a 3/4" and it's recommended a 5/8" flint be used. With the flint in that pic, the pan cover won't close completely.
When I acquire the correct size flint I'll see how it fits\works.
I suppose if I do have a problem with the top jaw striking the frizzen, I could file back the radius of the top jaw to prevent it from striking the frizzen.
In just "thinking out loud" I would think if I hammered the frizzen straight, that would cause more of a direct "hit" of the flint against the frizzen, causing a much shorter flint life as you have stated.
I can't see any detrimental effects if I need to reduce the top jaw radius, and that would allow the strike\energy of the flint to follow the curve of the frizzen. Of course, if I reduce the radius to much that could cause a problem.....but if I have to do that.......