Well gent's, once I "got into it" I decided to just drill out the breech "the regular way". I started with locating a hole on one side of the breech-tang. Even using a center drill the hole managed to walk on me.
So, I studied the previously posted hook-breech photos and decided I would file (elongate) the hole if needed. That's not a big deal as the bolt is simply holding the lock in place. I then, after much measuring, drilled the hole through the hook-breech. Now, before I did this I studied what the outcome would be. But I thought since the hook part takes the most abuse, the lower section just holds the barrel from going side to side. So I ended up with this:
Then I drilled the other side of the octagon and after some filing, the bolt goes through
Now, I haven't yet drilled the bolt hole through the side plate as I wanted to align where the bolt would be when I drill\tap the bolster. From this pic you may be able to see (bad pic angle) that the bolt needs to come forward maybe .030-.040 so that the bolster hole\tap will have enough metal around it to work properly. I'll do some filing on the hole(s) to make that work. The holes will be elongated but all they do is hold the lock in place. So I don't see that as a problem.
Edit: I haven't tried to remove the barrel with the lock bolt installed. I may have to reshape the hook-breech plug end similar to how Josh Johnson's has been filed. But since it's likely the lock will need to come off when cleaning occurs, I may just leave it as is.