One question about the 33" model that might shed some light on the 947' v. 938'. Did Jeffries build it himself or did one of the series' model makers build it? the reason I ask is that the studio may have just said to one of the builders, "Build a 33" model of this ship," which the model maker did without much knowledge of the actual final size of the ship. Jeffries, on the other hand, might have been a little more accurate in his scaling since he knew the exact length.
Just some food for thought or garbage for the trash can. YMMV.
BTW - Shaw, great work on this as usual. I can really appreciate your love for this project given the amount of research you put into it. Look at the page count for crying out loud - 77?! Shows you are getting some good response (if not always in agreement) and that you are serious about getting this done. Keep it up!