Flintlocks are all I hunt with anymore...bevel up or down depends on the size of the flint and the size/geometry of a lock.
In my locks, I use 3/4" x 7/8" Tom Fuller hand knapped black English flints...I start them out bevel up, but as they wear about halfway, I flip them over bevel down to continue getting the optimal frizzen imact angle and longer flint life.
Here is a new flint installed, ready to go:
