You can see in the interior shots of the engineering room of the refit-Enterprise looking back towards where the power conduits split off to the nacelles that there aren't any bracing structures reaching in. I'd guess from where the nacelle pylons connect to the secondary hull they only reach in for support about 1 or 2 decks at the most.
The neck connects to the wider torpedo launcher box but it's mostly hollow in the front leaving only a couple of points where there could be nice beefy vertical supports.
Anyway, all I'm saying that with advanced technology (including those of alien origin) there is alot of flexibility to build things we would normally think is impossible. (Or at least it could be argued that way
I'll stop here so as not to derail havoc92's progress.
Keep up the hard work havoc92