I hate having to ignore any evidence. I believe you'd also have to ignore the module added to the rear of the model (identified as the "aft crew lounge" on the MSD) at the same time as the bridge. It looks to be about five or six decks tall going by window rows.
A thought just occurred to me - in DS9's "Emissary" we see an Excelsior-class ship have the entire front of the saucer blasted away, in a manner not too dissimilar to the Enterprise's fate in STIII. I know that for the Enterprise an amazingly detailed wreck model was created, only for all that detail to be hidden beneath animated fire in the movie. Has anyone seen pictures of the wrecked Excelsior saucer model from "Emissary" (which IIRC was also used in the Star Trek: Borg
interactive movie game)? It would he interesting to see how many decks or details are visible.
Oh, and Scotty and Chekov standing in the Enterpise-B hull breach from Generatons
may be a useful size reference too.