I can shed a bit of light. The guy you really wanna talk to is jakb though, he owns all the pumps.
I own the
herc and
X-40, and I've used the
Hydromax x40 once. The new
gaiter on the
Hydromax models is larger so that is why your balls are getting sucked in. I had my balls getting sucked in with the
x40 when I used it, even though I fill the
X-40 on the first set.
I've used the
X-40 successfully as well. Bit of a learning curve to figure out how to use it without getting your nuts sucked in. I did scrotum stretches and placed the pump high up on my pelvis, so it sucked in my pelvis rather than my testes.
Jakb says the
penomet size is a bit smaller than the
x40 so you may wanna go with that. If you have the money, you'll want to move up incrementally.
I started pumping at 5.5" MEG. The
X-40 got me to 5.75" MEG but I could not get any more than that due to the size of the tube.. There was simply not enough circumference of pump for me to get the expansion to make any permanent gains above 5.75, even though my cock was probably 6.4" in the tube.
Depending on your size, you'll either want the
x40, the
penomet or the
x40. They give a dimensions chart of the
Bathmate products at the website.
In my case, I am getting the
x40, even though I know I will outgrow it very quickly. AFter that, I will likely get the
penomet, then once I have outgrown that, I will see if my
X-40 will give me the gains I need. IN other words, I'll see how close to the plastic my penis is in the
X-40 (penis closer to plastic tube = more gains). If I am still not thick enough for
X-40 to give me significant gains, I will get the
x40.
Not necessary to go that route. Just makes it easier and more efficient. If you're 6" erect girth, I'd say probably go for the
penomet, but do your research. Jakb says the suction is not as intense on the
penomet as it is for Bathmates.