Let me relate a bit of my experience here.
I pumped fairly regularly for a couple years, but unlike most guys, the more I pumped the more sensitive my blood vessels became. It got so bad that even 3 in hg was causing a LOT of red spots, and I had one dime size area that was so sensitive that it was becoming permanently darkened by the regular hemorrhages.
So, about a year ago (?) I quit pumping and started clamping. Clamping can also cause red dots, but I kept the pressure down and it was fine. I then started using a hair tie wrap (read the thread) as a condom, and it allowed me to use much higher pressure with minimal red dots.
This thread made me curious, so I broke out the pump and started to experiment. I used a max of 5 in hg for the first week, with slowly working up to 5 then immediately dropping to 0 or 1 or so. What I found was I was getting a couple red dots, but totally acceptable…and they were getting fewer with each session!
What this indicated to me was that the sustained vacuum was basically “inflating” my capillaries until they would start to burst, so by intermittent vacuum, it was allowing them to shrink back down before bursting…AND it was actually making them stronger to sustain greater vacuum!
I than began to experiment with longer holds at max, and found I was able to go longer and longer periods as long as I continued to drop vacuum to very low levels every minute or so, up to two minutes so far.
This is now the second time I went up to 6 in hg for two minutes at a time before backing off to about 1 in hg, and today I had almost ZERO red dots!
My point here is NOT that you should hold those very high levels for more than a second, rather that I have found that I am conditioning my blood vessels with intermittent vacuum (perhaps indirectly proving that it DOES toughen tissue). My reasons are that I want to slowly condition up to where I can begin to use this method safely, but if I ever get up above 8 in hg, I will certainly use the instant release recommendations.
OR
If I can condition my blood vessels, perhaps try to hit that 30-60 minutes at 5 in hg…which is a tried and proven approach by many vets (of course broken into small sets)
OR
Use this method of high intermittent vacuum once in a while, COMBINED with longer times at moderate vacuum more frequently that is well proven.
Anyway, just my thoughts.