I've sorted out the various pieces for each DN. The one shown in the first picture has had the lower saucer swapped out for one I had already installed the lower saucer deflector housing (a PNT part) - it needs to be secured in one corner better then the whole thing gets puttied. I've also changed that beautiful DLM lower saucer sensor housing to the PNT Abbe-type, which could be considered more having in common with the TOS style lower sensor array.
Pictures of the lower saucer will be coming later, in a few days.
The upper saucer has been almost completely puttied and is being sanded. What's left to be puttied will wait till I get the new DLM B/C deck in place. Thanks to CLBrown, I now know that this is still wrong. However... with *2* DNs on the table now, I just am not going to change it. Justification: The AMT kit is wrong, anyway! (man, that's pathetic!)
Modifications to the 2nd DN - which really wasn't intended to be covered here - have been started. I'll have to reinforce the vac pieces quite a bit to withstand the work and the stresses they will have to deal with later in an assembled state. A buddy of mine modified the dorsal to fit around the stock AMT dorsal, thereby fixing that whole strength/support issue.
Definitely not being covered here was last night's discovery of missing pieces for my through-deck conversion. How much was missing? Everything below the saucer. I was nearly driving myself nuts trying to figure out where that box got to!!!
Well, re: the B/C deck structure... just make it a ship which is not on the "list" and maybe treat it as a similar, but different, class. While the "Federation-class (uprated) Dreadnought" has the "fleet command center" there, it also has the enlarged secondary hull (with dual m/am reactors).
The ship you're building is SIMILAR to that, but has a smaller secondary hull (only one reactor), a smaller B/C deck superstructure (no fleet command center), a split impulse deck, and some different weapons hardpoints. It's clearly not the same class of ship.
Maybe the ship you're building is a "fast cruiser" rather than a "dreadnought?"
After all, "Dreadnought" does NOT mean "three engines." And there's no reason that a three-engine ship need be called a "dreadnought."
Personally, I never thought that the "Ascension-class Dreadnought" (with the "fleet command" functions but with much lower total power output) really qualified as a dreadnought, anyway. I'd have called that a "command cruiser," personally.
FYI, "Dreadnought" is a real naval term, and is really a subcategory of the "battleship" category. In general terms, a "dreadnought" is just a battleship with all the guns of equal (and large) sizes, rather than the distributed range of sizes "conventional" battleships usually carry. In other words, it's the "big guns" battleship, and (in real naval terms, again) was thus typically the centerpiece of a large fleet, relying on the supporting fleet to provide the smaller-weapons support, defending against smaller threats which it would be unable to defend itself adequately against. And yes, this would then TYPICALLY have been the HQ ship of that fleet.
In TREK terms, I always assumed that the extra engine was there to allow the very heavy ship to keep up with the rest of her fleet and to not maneuver like a sow in mud. The ship would be heavier, in large part, due to a much increased power generation system. That system, in turn, would permit the ship to fire highest-power weaponry at a nearly continuous-fire rate for long periods of time... in other words, making her the long-range-big-guns ship at the center of a fleet, much like the REAL "dreadnought" type ships would be.
Of course, this is all fictitious, so your mileage may vary... but I just choose to relate the "real world" definitions" to the "trek world definition" as closely as possible.
And as a result, I think your ship is likely not a "dreadnought" at all... but likely serves some other (albeit not totally dissimilar) combat role.