I had another one made basing it off the one that came with a crank,when it
needed a tighter ID, and a little more converter nose engagement for a 1/4" mid plate,...after talking to PTC.
I don't remember the final dimensions though.
Doesn't have to have a beveled shoulder,...could be squared. Just went with the bevel to be able to pry it out easier
Watch your bevel angle tho,...to make sure you have enough to register the flex plate.