THE NEBULA CLASS IS TO THE GALAXY CLASS AS THE Miranda/Soyuz/Reliant was to the Constitution Refit/Enterprise.  Employing a saucer section and warp nacelles almost identical to those of the the Galaxy, the Nebula also uses a similar design philosophy as the Miranda/Soyuz in that the warp nacelles are slung underneath the saucer on downward-sloping pylons, and there is a weapon/sensor structure projecting above the saucer behind the bridge.  One of several new designs that would be created for ST:TNG, the Nebula Class seems to be broken down into two distinct types, distinguishable by the style of pod that they sport above the ventral surface of the saucer.
        The first type, known for game purposes as the Mark I model, features a thin, oval-shaped structure that rides on two support stantions attached to the warp pylons.  This oval rides fairly high above and behind the bridge, and looks not just a little like the radomes on American AWACS jets of the 20th century.  Whether or not the oval structure on the Mark I is indeed some kind of advanced sensor unit or other kind of detection device is a matter of some debate among fans, but for the purposes of the game I have treated the oval as a benign, non-weaponry related structure, thus making the Mark I a science heavy cruiser.
        The second type—known on this site as the Mark II model—features a triangular, much thicker structure which is supported by a single heavy-duty pylon projecting out of the spine of the engineering hull.  Based on footage from numerous ST:TNG and ST:DS9 episodes, this triangular projection very often functions as a weaponry platform, much like the "roll bar" of the Soyuz/Miranda.   Official text from the creators of the ship indicates that the pod of the Mark II Nebula is a multi-role structure capable of taking interchangeable equipment, either sensory or weaponry.  For the sake of simplicity in the STSTCS system, I have treated the Mark II's dorsal pod as a weaponry platform, making the Mark II something of a heavy battle-cruiser; very different in mission from the Mark I.
        Also of some debate is whether or not the Nebula Class saucer section can detach from the rest of the ship, like the Galaxy's saucer, and whether or not the Nebula has a civilian population in addition to its Starfleet crew compliment.  Based on the research I have done, it would seem that the Nebula does not have a civilian compliment aboard, and I have never seen any writing or television footage indicating that the Nebula's saucer can fully detach from the rest of the ship.  (This makes my life easier only in that I don't have to fudge full blown stats for both saucer and stardrive as I did with the Galaxy.)
        In terms of game stats, I have treated the Nebula as being slightly less massive than the Galaxy, with the Mark I having much less combat weaponry than the Galaxy, and the Mark II having somewhat more combat weaponry than the Mark I Nebula.  Realistically, the Nebula would make a superior fighting ship as its compact size compared to the Galaxy makes it a smaller target, not to mention affording improved maneuverability.  But since the Nebula is a design of roughly the same age as the Galaxy, I have limited the Mark II model so as to not be more powerful than the super-advanced Sovereign Class.

        — BRT