ok, if this is supposed to be an earlier version of the D class, or a vessel in the same era but one class down, I really think those dvoridex engines need to go, they look far to modern compared to the TNG D class. Honestly, perhaps something along the lines of rod oniels tmp rommie could be stuck in there except light the grilles (much like they did on the excelcior)
anyways, I've attached some pix here. Firstly, the cicled part I think would look better if it was filled in an bulged out like the bottom of an oberth. The neck ought to go. You could have launchers or some kind of launch bay at the front edge of the bottom hull if you do the bulge idea (we never see any visable shuttlebays on the D) and that horrible looking front end you got on the head just looks dumb,a dn the "lip" around the area where the torp launcher is looks sorta like the cheesy robotic faces often given to transformer or robotic suit clad superhero face masks....ick!
Also, a wall between the 2 halves of the hull might still be a good idea, even if it is a pylon (thin) styled support and a fan-tail in the rear for visable impulse mounts (rather than having a single warp/impulse unit)
Ah, I see the confusion.... Actually the ship you adjusted in the pic is the NE, or the DDorax refit. NE comes after TNG. This is how I break the eras down....
EY:
Early years, from the phoenix onward to the next era, about 2000 to 2100
PF: Some people call this ENT, but I ignore the series, so instead I call it
Pre-Federation, the formative years. About 2100 to 2200 or so.
TOS:
The original series, 2200 to 2270
TMP:
The Motion Picture, 2270 to 2300
LE:
Lost Era, 2300 to 2350 or so. From the end of the original crew pictures to the beginning of TNG.
TNG:
The next generation, 2350 to 2400. This includes TNG, DS9, Voyager and the new crew movies up to Nemesis.
NE:
New Era, 2400 and beyond.
So, the DDorax with the engine pods is about early to mid TNG era, the one with the talons is NE, much newer, a refit. The one you want to show the changes on would be the one with the nacelles.
I also thought about doing a LE version, pre-TNG, showing older nacelles, perhaps no bottom. Something more along the lines of the TOS BOP.