Is 9 bar overrated? Certainly is. But darker the roast, lower pressure is better (in general). Just thinking: the reason why some people say, that small levers are good for dark roast only is, that they used their machines on low pressure. For lighter roast, the higher pressure is often necessary.
When I first tried Gabor's kit, I also realized, that although I was starting on 9bar, it quickly declined to 6, and stayed there for the bigger part of the shot. With the pressure gauge now I use both arms, to keep the pressure steady at 9bar.