I read this about four times, and found a description of where the CG is on a J3. And you're right. First, what I had been thinking of as "CG" is some point behind the rear seat, which is behind the trailing edge of the wing, and obviously can't be the CG. And second, I described something as a static condition where it's really dynamic. It's the vector of that point that has to stay within the wheel track to be able to keep the aircraft pointed forward.
There are a lot of people on here with way more tailwheel experience than me. I'm not claiming to be an expert, just stating that I don't think it's a difficult skill in general. I learned in a cub, have a hundred hours and more than 400 landings in them, took my first checkride in one, and am far from an expert. My point through all of this is that I don't believe tailwheel is a magical skill. I'm not suggesting anyone go out and get a paper endorsement and fly without adequate training, or that every aircraft flies the same.
Whenever tailwheel comes up there always seems to be a contingent that believes you have to be Bob Hoover to fly one, and that's just not the case. I think that mindset scares some people away, and that they're missing out on a lot of fun and a great learning experience by picking it up.