Enterprise-D center of mass

[The Silence and I]

Not quite. The only times we saw the saucer units operating during TNG's run was when the saucer was separated. The rest of the time, only the stardrive unit was lit.

Quite true (stupid, but true). Perhaps the other engine is close enough to the CoG that the saucer units needent operate at enough power to glow noticably...or maybie there is some funky warp drive thing. *snaps fingers* hey, the nacelles are nearly always lit at sublight, and they are the only harware I know of that can lighten the whole ship. I begin to suspect they can compensate for the impulse drives, making the effective CoG where-ever they want it. Of course this don't mean a thing in Booby Trap, as everything was shut down, so we do know where the actual CoG is.

[Major Diarrhia]

Not quite. The only times we saw the saucer units operating during TNG's run was when the saucer was separated. The rest of the time, only the stardrive unit was lit.

However, in DS9 Galaxies usually ran on all three impulse engines.

True, they were into more power during that war.

The thing is, there is no indication that the impulse engines need to be centered or that they creat thrust becaused they simply aren't centered. In just about every designe we've seen they are placed high above where you would expect them to be.