Today I took it all the way up to 10 in hg, which for me is very, very high.
I did all week last week ( 4 days) up to 6 in hg, worked my way up to first 7 in hg then 8, etc until I reached 10 in hg. I would stop and check periodically for red dots, got just a few so I continued.
Because that is so high for me, I was VERY CAREFUL to quickly get up to 10 then INSTANTLY release vacuum back down to about 2 in hg.
I did about a total of ten minutes and finished with very few red dots, which is remarkable for me.
I have started doing the same as you, sparky (ie 10mins, up to 10:Hg and immediate release to about 2 -3” ). Been doing it for about a week without any red spots or other issues.
At the end I have started ‘milking’ the cylinder as suggested by Gprent in the earlier thread “Cycling pressure up and down…work those ligs baby!”. By instantaneously pulling the cylinder a bit and releasing it without loosing vacuum I was able to vary the vacuum in the range 5 - 8 ” Hg in rapid succession. I also kegel while in the cylinder and find it has a slight measurable effect on the vacuum.
My motivation in this is as much to improve EQ as well as a larger penis. I combine it with extending.