Harder erections does not equal a larger penis. You`re just fulfilling you full potential, so to speak. I suspect that this could be the case for a lot of manual penis extension exercises also. (jelqing etc.) Guys are improving their erections in terms of hardness and duration, but that does not mean they actually increase their penis size. I have yet to see any evidence that is credible that proves this is possible.
We will stomp to the top with the wind in our teeth.
George L. Mallory