Marcus, I don't think you need to worry about drawings by George Campbell.
He was a naval architect by training, an excellent draftsman, and a conscientious researcher. As I remember, he drew the plans for the Model Shipways Newsboy, Phantom, Rattlesnake, America - and probably a couple of others that I've forgotten. He also wrote books of his own (China Tea Clippers and The Neophyte Shipmodeler's Jackstay are the best known), and dabbled in marine painting. (This link may be of interest: http://www.bbc.co.uk/arts/yourpaintings/artists/george-f-campbell .) I never met him, but I can remember when he was in his prime. He was widely known as an immensely knowledgable man and a first-rate, congenial gentleman.
His most famous set of plans may be the ones for HMS Victory, for C. Nepean Longridge's book The Anatomy of Nelson's Ships. (Mr. Campbell also did all the superb sketches and drawings in the book itself.
When Smithsonian Institution decided to commission a big model of the Constitution, it commissioned Mr. Campbell to draw the plans. (At that time Howard I. Chapelle was in charge of such projects at the Smithsonian; I imagine he was the one who picked Mr. Campbell.) Those drawings, of course, became the basis of the Revell 1/96 kit.
He was the naval architect in charge of the Cutty Sark restoration project in the early 1960s, and his plans of her are still available (one of the biggest bargains in ship modeling). Those drawings were published, if I remember right, in 1962 or thereabouts. The Revell 1/96 kit had been released in 1959. I don't think Mr. Campbell had anything to do with it - but I could be mistaken.
Historical research is an ongoing process; every year historians turn up new information about something. Mr. Campbell's Victory plans don't show the raised forecastle bulwarks, the third cheek knee, or various other details that are now thought to have been on the ship at Trafalgar. There seems to be a small industry of scholars and modelers dedicated to figuring out exactly what the Constitution looked like in 1812, and they've dredged up some interesting little details that Mr. Campbell's drawings don't show. From what I can gather, though, none of those revelations has been particularly dramatic. (Maybe the most visible one is the fact that she didn't have hinged gunport lids.) Mr. Campbell's drawings - and the Revell kit - look darned good to me in terms of accuracy. And I'm sure the recent (post-fire) restoration of the Cutty Sark has revealed some discrepancies with the Campbell drawings. But I'd be surprised if they amounted to much.
Any sensible researcher knows that the next generation of researchers is likely to come up with some material that he/she missed. That's how the field works. (If I were - heaven forbid - to build another model of the frigate Hancock, I'd use a different shade of red paint, leave off the bulwark pinrails, and...oh, never mind.)
The last time I saw Mr. Campbell's plans for the Model Shipways America was more than thirty years ago. I do remember studying them for some time, and finding them fascinating. I particularly remember a note about how the ship's sheer had changed over the years. I think you'd be quite safe in basing a model of the ship on those plans.
Finding them is another matter. I googled "Yacht America Plans," and came up with quite a few images (including what I'm sure is an illegal copy of the Bluejacked plans and instruction book). But all I could find about the Model Shipways kit was a few photos of the box contents and a finished model (which looked excellent).
I also think the Bluejacket plans are excellent. (I won't dignify the website by listing it here. Nic - I don't blame you for being irritated that such a thing is on the web.) I'd be interested to know how much difference there is between the Bluejacket and Model Shipways plans. My guess: scarcely any.
I think you're perfectly safe with either of those sets of drawings.