You must read more about those ships. Sprignfield is an older design which carries older warp drive. She was abandoned for production because of one defetc. Her connection pylons to her under pod were under the stress while in WARP. NO class was commissioned later and was a test bed for Galaxy like warp drive. That is why her engines are longer then galaxies in comparison. NO had a teething troubles with her warp coils. Springfield was indirect predecessor to NO which later carried some of Springfields duties
Reference:
http://www.ditl.org/
Aah, the incomprehensible pile of complete and utter bollocks that is DITL.org - what you just quoted is pure speculation pulled out of that site author's arse. The Springfield doesn't even have that pod on the underside - that was assumed from a single badly scanned, printed, photocopied, scanned again, colourised photo from a decade old slideshow and the guy who built the Springfield admitted the pod was just stuck on to make the ship rest properly on the coffe cup they put it on
the New Orleans and Springfield are both clearly from the same era along with the Cheyenne and the Challenger, they are all derivatives of the Galaxy design program from the 2350s and 2360s.
The 'A Call for Duty' site also seem to be fans of pulling stuff out of their proverbial orifices as transwarp was a failed experiment with the Excelsior class over half a centruy before the Springfield class was even designed.
There seems to be a strange secondary hull between the saucer and the TNG coffee cup in the side view. This could be a pod similar to that of the Oberth, or just something attached to the model with adhesive tape - maybe to stabilize it to take a better photo. Ed Miarecki recently confirmed that he actually added such a hull to the model
from the EAS article on the Springfield:
http://www.ex-astris-scientia.org/articles/springfield.htmAlso take a look at the studio model:
http://www.ex-astris-scientia.org/articles/wolf359/springfield-cheyenne-okuda.jpgI dunno about you but I see no secondary hull at all, the model's shadow is way to close to the model and it completely disappears a fair bit behind the side of the saucer suggesting that it is resting directly on the table, on the site they reckon it was removed just for this photo but I see no reason why.
P.S. this has gotten way off topic - someone make that Merced!