Clamping and EU's are extremely high risk. This is for very advanced PEers who have a great deal of experience doing girth work.
You have to be in touch with your body, to know your limits. It takes experience to master it.
Once you get to a certain level, and are ready to try clamping or EU's, you have to start out slowly and with extreme caution. You have to get a feel for how your body is responding, and react accordingly. You have to be on high alert, because things can go wrong very quickly under such high pressure.
I will tell you all a quick story.
For those of you who don't know, EU's, or Extreme Uli's, are similar to clamping, except you are using flexible PVC tubing and a hose clamp to tighten down. Anyway, I had bought a screwdriver to tighten and loosen the hose clamp.
One day, I was on my second 10-minute set. My shaft looked and felt like it was about to burst, and it was time to remove the device, at around the 8 minute mark. So I went to reach for my screwdriver that I would keep on my bed. I ran my hand over the bottom part of my mattress where it was supposed to be, but it wasn't there. I quickly jerked my comforter off of my bed to find the screwdriver. It was nowhere in sight. At this point, my mind automatically went into survival mode. I knew I was in very serious trouble, and I couldn't think straight. My heart was literally pounding, like it was about to burst out of my chest. The adrenaline rush was in full effect. In a moment of clarity, I looked towards the end of my mattress, where it intersected with my wall. The screwdriver was hidden in that little space between the edge of my mattress and my wall. Somehow it made its way there.
I grabbed the screwdriver and got the device off as quickly as I could, which took more time than usual, because my hands were literally shaking the whole time. When I got that thing off, I quickly checked to see if I still had feeling, to see if everything was fine. Thankfully, everything was okay.
Those were the scariest 20 seconds of my entire PE career.
That was the last time I ever did EU's.