Popman - Many thanks! The Hancock model is based directly on the drawings of Howard I. Chapelle, which were published in his book, The History of the American Sailing Navy, back in 1949.
Chapelle was Curator of Transportation at the Smithsonian Institution, to which he left all (I think) of his original drawings. The Smithsonian sells blueline copies. When I was getting ready to build that model I ordered copies of those particular drawings, which include the hull lines, outboard and inboard profiles, a scrap view of the transom, and deck plans (no masts or rigging). The prints were on 1/48 scale; I took them to an architectural drafting firm (this was in about 1977 - before big, reducing photocopy machines were common) and had them reduced photographically. I bought lots of copies, and cut them up to make templates.
Chapelle apparently traced (and to some extent cleaned up) the Admiralty drawings made by the British after the ship's capture. The originals (on drafting cloth) are part of the collection at the National Maritime Museum in Greenwich, London. They've been reproduced in several books and articles. I kept one of those reproductions on hand as a check on Chapelle, who had a nasty habit of changing small features he found on old plans because he thought they didn't make sense. (More recent research has established that he was often mistaken.) The most prominent example in this case was the shape of the ship's bow at the level of the forecastle deck. As can be seen in the model photos, it has a rather odd, curved configuration that Chapelle, for some reason, didn't copy quite right in his plans. He also added some questionable details (gratings in the platforms at the end of the gangways, for instance) and omitted others. (The Admiralty deck plans show the thickness of the bulwarks. Chapelle doesn't.)
Chapelle's drawings are far easier to work from than the original Admiralty ones. (Eighteenth-century drafting cloth has stretched and shrunk by now, and those old draftsmen were notorious for their use of ivory rulers and scales. Ivory is slightly hygroscopic; measurements taken with instruments like that aren't to be relied upon.) My suggestion to any modern modeler dealing with a subject that's covered in a Chapelle drawing: use Chapelle as your working drawings, but check on his sources if possible.
Contemporary eighteenth-century sail plans are rare. For my little Hancock model I used the spar dimensions of the frigate Raleigh, which was built at the same time in Portsmouth, New Hampshire (not far from Newburyport, Massachusetts, where the Hancock was built). The Raleigh's spar dimensions are included in a fascinating "Inventory" of her equipment that was published years ago in The American Neptune.
There's one other contemporary pictorial source regarding the Hancock: a series of four oil paintings, believed to be the work of Francis Holman, now in the Peabody-Essex Museum of Salem, Massachusetts. The paintings depict the battle in which the Hancock was captured; they may have been commissioned by the captain of H.M.S. Flora, one of the British ships involved in the action. Those paintings don't show the Hancock in much detail (and they represent her inconsistently), but looking at them at least brings the modeler a little closer to the subject.
I suspect that's more than anybody wanted to know about this topic - especially in a thread that started out concentrating on the Constitution's gunport lids. Sorry about that.