A long belated thanks for answering this Xotl! Your answer coincided with my self imposed exile, and I was less than 100% diligent in answering things from that time.
I'll see what i can do to get the cognitive dissonance resolved. The 3 vs. 4 thing has wide ranging implications for aerospace craft design (i.e., 2/3 or 3/5 being the minimum thrust necessary to make orbit). The most interesting possible answer would be 2/3 Aerodyne craft being able to pull it off (perhaps with some stomach churning maneuvering), but not spheroids. That would make the cost multiplier difference between the two more meaningful.
