Chief, I have an old friend that has sleeved many a double shotgun in his shop over the past 40 years using the Damascus monoblock, usually drops down a gauge to make sure that there is enough meat on the monoblock to make the seam easier to finish.

I picked up a book last year "Building Double Rifles on Shotgun Frames",by W. Ellis Brown. Makes interesting reading, if you are inteested in the techniques used.