Glad to help. No where near as critical but it can make in-flight trimming and performance better.

I may just have to put together one of those Vanessa contraptions and play around.

By the way: God and nature do not determine where the center-of-gravity should be. The "suggested" spot is where the designer/builder decided his model flew as he thought it should. Most designs have a relatively wide parameter and some a narrow one. It is usually better to be conservative and start out nose heavy. Because, as the old saying goes, "A nose heavy plane flies poorly. A tail heavy plane flies once."

I happen to like doing inverted flat spins and that works best with a "neutral" C.O.G.; usually near the rearward recommended range.

Here's a simple test for C.O.G. trim. Set the throttle so the model is flying level. Now bank to 45º and center the controls. If the model quickly noses down you are nose heavy. If it noses up you are tail heavy. If it stays in level flight for a three count and then noses down you are about optimally trimmed.

And, as someone mentioned earlier, the fuel in your tank is always additional nose weight. The above trim will change as the tank empties, so try it several times during a flight before making weight corrections.

And, always, do what you can to adjust the balance without adding weight. Move the battery, shift servos if possible, play with the gear. Remember lighter flies better.