Here is a link to a set of Fw 190A-8 blueprints you can buy,
http://www.aircraft-manuals.com/fowufwa8aibl.htmlHere is a quote from the site;
"From the original manufacturing drawings converted first on microfilm and now in electronic format Airframe Engineering Drawings ( Blueprints ) Tiff and PDF Graphic format # 900 Engineering drawings sheets This set contains drawings for most aspects of this aircraft - Bremen blueprints for the Fuselage and Wings, Rudder, elevator, canopy, windscreen, cockpit, formers, ribs, instrument panel and supporting structures, cockpit side panel, control linkages, cockpit controls, dimensions between ribs and formers, wing riveting plans, maintenance access panels. Included are very accurate fuselage cross sections with data co-ordinates for the curves. This Set of Engineering Drawings are not complete or exhaustive."
This would be a very good start for an accurate model.
I don't know where HTC got their data but at worst case they could get all the data by simply going to an existing airframe and getting all the measurements. That would be a very long and tedious process, but it could be done.