Well.....after my initial "oh shucks" (Actually words similar to that) I started to think (always dangerous) and surf the web a bit.
My thinking is if I were to plan this from the start, I'd go with a 45 cal (that's the minimum legal for deer in Pa)...and if I went with a 45 cal I'd likely go with a smaller barrel for the weight savings. (Albeit, I don't know the weight difference....but there has to be a difference).
Then I was thinking, since I'm making a smaller version.....could I still do this with the existing stock and the existing work I've done for the hook breech?
The hook breech "issue" would be: Even though I could use the hook\plug that I fabricated, the problem may be on the hook tang. I filed a grove in the tang for the hook to lock into...and if I went to a 13/16th barrel from a 15/16th barrel, I'd have to remove about .055 of metal from the top tang...and right now I don't know how much metal will remain from that point, to the top of the "underneath" grove. I may just need to acquire another tang hook....or I could make another one. I have the experience.
Of course, a 7/8th barrel could always be an option.
I took a quick look at the stock, and I think I could still use it going with a 13\16 barrel. I grabbed my old T\C half stock, and lined up the bottom of the T\C barrel channel with the bottom of the stocks RR hole. I took this pic below. This will require cutting a new barrel channel (no big deal) and drilling a RR hole....something I've not done before but I'm sure I could handle.
This pic doesn't show the butt end, but there's plenty of wood on that side as well.