http://www.starshipmodeler.com/trek/neb_db.htm

Not that this model is very accurate with the studio model, but one important feature that I noticed was the fairly correct placement of the impulse engines (not those saucer impulse engines, but the smaller vents at the rear of the saucer). These are the actual locations that are present on the Nebula studio model, although we've rarely seen them lit onscreen. Wish they would have left off the saucer impulse engines.