I appreciate the information! I have been going in semi erect. I have had little blood spots on my penis. I’ve been pumping too hard it seems, so I’m going to have to simmer down a little. I’m going to try fully erect.
That is definitely a sign of too low of an internal positive blood volume pressure and way too high of an external negative vacuum pressure. The negative volume pressure will cause the fluid from the subdermal layers (your skin layers) to surface. You can enter the pump flaccid, but before you pump past -4inHg, make sure your penis is fully erected. You then have to gingerly go up in pressure from there. Do you know that some brothers can get blister even at -4inHg for vacuum pressure even though that's the average baseline erection pressure? In reality, some brothers can get an internal erection pressure as low as +2inHg. So that extra 2inHg can indeed cause blistering.