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I don't know if any of us has ever used A2 or not.
O1 can be milled down or just filed down. Try filing it. If it bites it isn't hardened.

keep in mind that the thickness of the spine should be between 1/3 and 1/4 of the width of the blade. That is an often made mistake.

I had some issues several years ago but switing to short hammer handles with a heavy head changed that. Less rebound energy and less wrist strain

If it makes you feel any better, I still do all my work without a power hammer. :)