I have no idea what pressure flaking is or how to do it. Sounds interesting though. Right now, am just busting rock with brute force. I hear you on the flakes being too thin, have tried several, that where super thin and sharp, but shattered in the first couple shots, conversely many of my big nice flakes are too thick, barely fit in the cock jaws, but try to thin them or knock some off of them, and they shatter into rubble. Some are also, not the right consistency, spark great, but have almost a sandstone like texture, and ends up chipping, erroding, and/or crumbling too quickly. Some of my best flints just get too dull after a while (40-80 shots), the edges look smooth and or rounded, almost polished, busted one rock open, and it turned out to be some sort of (probably quartz) crystal.