Heretical though it may seem to suggest such a thing, I think the person responsible for that e-mail from the Smithsonian may have made a mistake.
Howard Hoffman is (or used to be; I have no idea whether he's still around) a curatorial technician in the Smithsonian's Division of Naval History. I met him a couple of times, quite a few years ago (at least 25 years, that is). He got his start as an airplane modeler, and got into ships as a result of working at the Smithsonian. His biggest project, so far as I know, was the beautiful, large-scale model of the gunboat Philadelphia that used to be exhibited there. (I don't know whether it still is or not; I hope so.) The remains of the real Philadelphia are in the Smithsonian; Howard made an extraordinarily detailed set of drawings of every part of her, then built the model as a means of showing the public what she looked like when she was in service.
My guess is that Howard may have made some additional annotations or amendments to the Constitution drawings, but I frankly find it hard to believe that he prepared a completely new set of plans for her. (I guess it's possible, but why would the Smithsonian have called on him to do such a thing? Since the death of Howard I. Chapelle the place has gotten progressively less interested in ship models; I don't think it's commissioned a new one in at least thirty years.) At any rate, Howard is/was a first-rate researcher and a fine draftsman; if he did make a contribution to the Constitution plans I'm sure it's a good one.
My suggestion: wait till the catalog comes. Unless it's been heavily revised since the last edition I saw, the Campbell plans are in it.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.