Neat diagram! You're right, it might indeed make for an interesting comparison to do the weigh-and-measure calculation using both my bathroom scale and the more accurate HF digital scale. If nothing else, it will give me some practice using this method in the 10 days or so before my trip to the US.
Again, being a stickler for words (after all I am a professor of linguistics), I always "knew" the CG...because it was printed right there in the manual.
Someone somewhere decided that the CG for this model should be at 124mm back from the LE. All I've done here is see how the model hangs when I prop it up at that location. It doesn't quite "balance" at the indicated CG, specifically, the nose is heavy ("down") and the tail seems too high the air. It would probably be flyable like this.
If I want the model to hang level (or at least what I perceive as level), then I need to move the fulcrum point forward about one inch...or I can achieve the same thing if I leave the fulcrum point at 124mm and place a 50g weight on the tail. To be honest, I'm a bit torn between just using the CG given in the manual (124mm) and doing the maiden with the model in its current nose-down attitude or adding a bit of weight to the tail to get a better visual balance on the bench, which is in effect shifting the model more towards a tail-heavy state. Due to a couple of really nasty tail-heavy maidens in the past, I tend to be perhaps overly cautious and set up my models with a distinct nose-down "balance."