OTOH, an even deck spacing might be fallacy, considering that the portholes (?) aren't spaced evenly, either.
Basically, the sphere has five or six rows of portholes, plus a few stragglers. Might be there are five or six habitable, roughly 3 m high decks inside, plus machinery in between them, and then some connecting staircases that have individual portholes between decks. On each deck, the portholes are nicely centered or positioned at eye level...
As long as we're arbitrarily picking a size for the ship, we could play with the original size of the components (space shuttle SRBs for engine nacelles, ET for secondary hull) and decide the ship is 53 meters long?

The connecting neck would still be of walking height then, while the large rectangles taped to the outer hull would be practical pod bay hatches for HAL to open and close. And a typical porthole would be about 30 cm x 60 cm, not all that different from what they had on NX-01. The sphere might have four decks (each with its own well-defined row of portholes, plus some additional holes at the floor level of Deck 2 below the pennants (possibly floodlights for making the pennants visible), plus an observation dome atop Deck 1.
Timo Saloniemi