I had an 11/16" cheap short 6-point socket.
I lame-handed grinding-wheel (Harbor Freight) ground the opening edge/circumference flat, just a little.
It takes off (and/installs) the flat/thin-head flywheel nuts quite easily (every time, so far).
Cheap and easy peasy lemon squezy.
For old times sake, I use the old style bolt locks (if I have good ones).
