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I might have suspected that you would be the one to zero in on my secret X-factor. The weight of the engine is probably the single factor most responsible for my savings on weight. The Jabiru 3300 is quite a bit lighter than the O-200. All up weight for the engine is approx 180 pounds, including all accessories, cooling and exhaust, so I cheated a little bit relative to you and others who have more standard engine installations. Also, my prop and spinner together are less than 8 pounds and I don't have that heavy prop extension (Well, I guess I do still have it, but it is in a box in my basement, not on the airplane).
As far as the paint cg goes, the computation is fairly rigorous numerically, so I doubt any errors there, but the tail has a lot of area, so does contribute significantly more than one might think. The forward face of the main wing is mounted at FS 78.5", so FS 70' would be hanging from the tip of the pilot's nose in level flight. Now that you mention it, though it may be fairly simple for me to break down the weight and CG of the paint on each subset of the airframe then report back.
On second thought, I do not want to cause Jim Masal any more stress than necessary, so I maybe I should just use the time to glue on another piece of hardware ;-) Tick-tock, right Jim?