@Mytran - Found an older image but I think this is relevant.
The image below is scaled at 355m for the TMP Enterprise but I think my comments are applicable for the 305m as well.
The two points of interest are the torpedo and engineering hull airlocks. The torpedo airlock is on the same level as the torpedo room deck which would put those windows next to it at "hip level". The engineering hull airlock however is above the cargo deck and necessitates a down ramp. That would put the windows at head level.
I believe because the windows aren't consistently applied relative to fixed airlocks that in the case of the engineering hull they can be independent of the deck height. On some upper decks the windows could be head height while the lower decks could be closer to leg height. So to me the internal decks of 12' still works at 355m because I'm not seeing a direct correlation of windows to deck height location, if you know what I mean.
Note: The 305m ship with 12' decks there is some "float" of the windows. The 3 forward-most windows on the deck above the engineering airlock deck are higher on the deck (like 10' up) while the other windows on the other decks are at head level (6').