And the saucer looks much more like a Galaxy's than an Ambassador's. Isn't there a top view of at least one of those ships showing that the saucer is elliptical, not circular?
And there is, sort of, some proof on the Freedom. There's a vidcap from TBoBW of a ship that some people have matched to the shape of the Freedom. It isn't utterly conclusive, but it suggests that the FF diagram is probably at least close.
------------------ "Back in the 14th century, stair-stepping to the oldies was not considered manly." -John Scalzi, on the longbow as the best weapon of the second millennium