Welcome the to campfire, EGSavage. I've heard of guys making shims for the lower tang before. Seems like it would work as well as the suggestion to remove a tiny bit of wood on the upper tang. Goal is to move the recoil pressure to the side panels and lower tang - both of which are less likely to crack.
And +1 to LBK.. though I think it's several factors. Orientation of the grain is a big one, plus how tight the stock is, plus how much pressure is on the upper tang versus the side panels and lower tang, plus how often it's fired.
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