My friend Sarah in Portland tried that vinegar trick with her apple pie last fall. She used a full tablespoon by mistake, and the crust came out so brittle it shattered when she cut it. I wonder if the amount is the key, because @michael_wood32 had a toughness problem too. Sarah's second try with just a tiny bit, maybe half a teaspoon, was much better and gave it a nice flake. Those old family tips really need some careful testing.