David can speak for himself, but I don't think you need to install the tang and sent it along with the barrel. All he needs is the barrel without the tang. If fact, I think that tang is just something that he has to deal with, and is an item that can easily be lost in shipping etc.
Very uniform file work. I like the square corner at the lug too. Your rear lock bolt will almost certainly be completely within the lug, it being so deep.