He did mention a Super Skybolt that does have two center ribs. The point I'm trying to make is that you really don't need to make this overly complicated. You really only need to get the CG into the safe zone and then go fly. Once you fly the airplane you can determine the optimal CG location. Those of you who set the CG once get the airplane up in the air and push the trim levers to get hands off at a certain throttle setting and call it trimmed are robbing yourselves of an airplane that could be flying much better. IMO it's much better to learn advanced trimming teciniques, your airplanes will fly better, easier and will be around longer.