Oh yeah, one more thing. I am drawing these 2D plans based on a deck-to-deck height of 3.5 meters. That's 2.75 meters (9') of head-height on each deck with 0.75 meters (2.5') of between-deck space for piping, wiring and ductwork.
What about Jeffries tubes, you ask? Well, I never have understood why you would need half a meter or more of crawlspace between every square inch of every deck. Certainly there are Jeffries tubes and crawlspaces but only where they are needed. I figure any special areas that require more than 9' of head-height would simply expand to 2 decks tall.
Using 3.5 meters, the ship is currently exactly 25 decks tall.