I used a pump for about three months, then went to the injections. What I discovered was:
1. Shaving helps alot. If you have a lot of hair, it breaks the vacum seal. I also tried shaving cream instead of KY Jelly, didn't help.
2. You need to pump for awhile, stop and let the blood rush in. Then pump some more. I was able to get to 21 CM in length but it took about 15 minutes. My girth almost completely filled the tube.
3. I also had to go to double rings to retain the hardness. That and the "hinge" effect was what made me go to injections. I will never go back to the pump.
With practice and experience, it will get better.