Transvaal,Your Idea of the shoe lump is a very good one.It's a sound method of joining a pair of barrels together and a lot of the early double rifles had barrels of that construction.As you say its a matter of method.When you joint the barrels in,you let them in without the hook being cut completely away.Let them down on the Draw and then cut the hook properly using a cutter through the crosspin hole in the action while the two parts are together.Doing it this way mean's the Barrels and action are exactly where you need them to be when the hook is cut.If your cutter is a few thou smaller than your crosspin,then it make's for minimal fitting,and then black the barrels down the last few thou to get them exactly where you want them.

Brennon,I hope you get what you want.Ian will certainly have the rising bite parts but whether he'll sell you any is a different matter.I say that as if he sold them to other's then no-one would be buying them from Rigby's.Best wishes with it.You have a Mammoth task ahead.