My English must be worse than I'd like to believe.
I only relied on Kimble's and Big Jim Slade's stern views of the saucer (diameter size figures supposedly undisputed) to arrive at a workable "real-life" width of the impulse engines' exhaust nozzles.
Next, I relied exclusively on the actual stern view images. It's easy to calculate the width of the skegs (and the dorsal in that area) based on the width of the impulse engines' exhaust nozzles.
Since the outermost port and starboard edges of these exhaust nozzles
are actually closer to the camera / viewer than the skegs, the area between the skegs is at least
8.5 meters / 27.9 feet wide.
This has nothing
to do with preference.
Preference would be assuming that the skegs are not just parallel to one another but follow a basic ovoid / convex shape of the dorsal which reaches a wider
point below the impulse deflection crystal...and possibly wide enough to accomodate both an impulse engine room and an engine core tower that would look something like this: