The idea was just to get across that it wouldnt be solid, if we realy really wanted we could take every 2 sections, use the bottom 2 blocks for redstone/floor and the remainder for the room:
________
|________ 1 - ceiling
| 2 - empty
| 3 - empty
| 4 - empty
|________ 5 - empty
|________ 6 - floor
|redstone 7 - redstone room
|________ 8 - ceiling of deck below
Which corresponds nicely to the already existing frame, leaves room for a little redstone fun, and gives us fair sized hallways. it ALSO cuts the total number of floors to 15, so it doesnt come without drawbacks.