Lemain, post 1108, your comments about the need to make a whole section and cut a panel from it make sense to me. On reflection it seems odd to me that Boeing did not make a complete sacrificial shell, either now, or in the past as part of the development plan.
Airliners do get all sorts of knocks - just recently a BA 787 was slightly damaged by a set of flying steps borne by high winds which had been predicted at least 3 days earlier!
Perhaps Boeing did contemplate a donor hull but this was by-passed due to project delays.