@ Lord Garth
All the TOS corridor and room wall panels had a maximal height or beam of 10 feet. And while we do have a couple of shots in TOS that exposed the full height, the overscan of any 4:3 TV tube set would have cut off some of the overhead areas.
An interesting piece is the briefing room set
. The top of the ceiling support beams ended at a height of 2.8 meters. I interpreted this as a hint that 2.8 meters was intended to be the average deck height in the saucer hull