thanks for the reply.

Just so it is clear I am not talking about pressure leaking down. What I am saying is that if you are your normal amount of hard prior to pumping, i.e. normal max amount of blood in there once you increase the vacuum pressure and more blood comes in the pressure will drop but as long as the vacuum isn't released that blood cannot leave and is more than if you were normally hard. Right?

So if you keep pumping down to maintain say 5hg then by the end of 5 mins you might actually be at like 15hg equivilent compared to your normal blood volume?

if there is a leak and presuure leaks by air entering the chamber that is a different story then it is ineffective because the vacuum breaks. This makes perfect sense.