I kinda considered that the issue with box length would be a self solving problem due to twist.
Oddly enough, just got a call from the dude who is building the rifle, and has the tube. We got to talking about other stuff, then I asked him about the barrel. He either told me wrong, or I heard wrong, months ago when we fist discussed it, but he assured me its a 9 twist.
So it IS 9 twist? And free? Even better! You must be living right