For me, there is a very difficult balance between the correct amount of blood in the head. If there is too little, the hanger wants to slip off. If there is too much, I get a pressurized feeling of pain in the head like you described. My first set, there is not enough blood so I do a light warm-up hang of 5 pounds for a few minutes. Then I take off the hanger and in a few moments, the head fills up with blood because of the light pains of hanging. I then squeeze out the right amount of blood back into the shaft with my hand until I have the right amount left in the head. Then I can do heavy weight, from 15-20 pounds with no problem. When I take off the hanger for a break between sets, the blood flows back in, so I again squeeze the head to get the right “pressure”- kind of like a bike tire. Experiment with the amount of blood you have in your head while you hang.