@Albertese - Thanks. I'll put together something for the tapered pipe set with some measurements for you in the next day or so. Keep in mind that my model is a "best guess" so it isn't a final say on the dimensions of what that prop is
@Mytran - Here is a rough blocking out of what I think the primary hull engine room / impulse deck could look like. It takes the "twin jets" model but keeps it to a single engine control room. I tried to keep to what was seen on screen and expand out from it. It's subject to change as I watch more of the episodes (one by one!)
I've put it on Deck 5 and left enough room for the S2 Engine Room to poke up into Deck 3. There is a large gap on deck 6 below the engine room for the turbolift shafts and other access ways to go through.
I did bend the entrance a bit and retained that side corridor that Scotty runs to and from to get to a jeffries tube.
A power conduit (ala TMP) runs up from the mains to power the impulse engines and also distribute power to the primary hull. In "The Ultimate Computer", I figure M5 taps into this power bank