While it is only 3x8, my wife can run all 8 off the middle chainring, without FD rub... barely. Efficiency sounds nice, but what you are saying is that a 1x9 with a properly setup chainline only gets 4 gears? Kids across the street are running 1x11 on their mountain bikes.

Even if in a theoretical, or your commuting experience, it is the best efficiency, I find it hard to imagine how you are not prematurely wearing out your chainrings when you are in a tweeter ratio between 2 chainrings.

John