"I do run into some hard sticky clay around here."
Twelve inch, for sure. I have a thin layer of "topsoil" (pretty heavy, stick stuff), followed by yellow clay, with grey clay under that. Never had a problem with the stuff dropping out of the 12-inch BH on my BX23.
As far as digging force, the BX23 BH has plenty of power -- at first you may find yourself wishing you had a couple thousand pounds of extra tractor to handle it! /forums/images/graemlins/shocked.gif Once you practice a bit, though, you'll be able to dig like a champ without pulling yourself all over the place.
Welcome to the family! /forums/images/graemlins/grin.gif