Since the F-1211A is the thinner of the 2, I placed the manufactured head on that side and the shop head on the F-1211B side. (The exception was the flush rivets, which are countersunk on the F-1211B side.)
Unless the plans say otherwise, normally the manufactured head goes on the thinner material. However, I've seen photos of guys who have put the manufactured head on the F-1211B side. In this case, I think either way is acceptable because both of those parts are made from fairly thick material.