This sounds similar to condom pumping that was being tried awhile back.
Anybody want to give it a try, to explain in detail just exactly what is going on here? But the created vacuum is a bit too strong.
Abco Research Associates has marketed and sold the machine since 1998.
However, this design does require a bit of knowledge to wire the circuit properly but it is somewhat safe using low voltage DC and certainly safer than line voltage 120VAC or 240VAC.
I would say if you have the V2000 unit, you need to get this sleeve.
Much better, and you can really get into feeling it as it moves up and down on your male member.