Pumping hard can put intense pressure on the delicate capillaries that line the skin. Some people have better tolerances of capillary pressure than others. It's really about the incidence of diabetes in one's family history. Diabetes makes it difficult for wounds to heal below the belt.
One may not have
full blown diabetes, but carry the type-2 gene and suffer absolutely no symptoms of the disease. These people might not be or feel like a diabetic, but their bodies are running on empty in the fight to stave off the disease and will most likely succumb to it sooner or later. Diabetics are at a high risk to develop atherosclerosis or peripheral vascular disease... it's the high glucose levels that destroy arteries, science isn't sure exactly why, but it is the reality. More than half of the amputations done in the United States are a consequence of diabetes. Coupled with Nueropathy (diabetes destroys nerves too and can wreak havoc on the nerves that communicate with the brain) which is one of the leading causes of impotence in diabetic men, the blood vessel damage can be a one way ticket to impotence town.
I have found that the presence of the diabetic gene in one's DNA is the single most important factor in a pumper's success. Pumping is really difficult for diabetics and pre-diabetics because of the capillary trauma that can so easily occur in the environment of early forms of peripheral vascular disease. It is the main reason that I pump soft, I don't stay soft though... I just don't pump for pleasure and am maybe semi-hard most of the time.
I would start out with a hard cock when I enter the tube, but relax my erection into the session. I am fond of using a vibrator or massager on the tube during my sessions to replenish my tissues with oxygen and fresh blood rather than jacking the tube to maintain circulation, but you should experiment with what works best for you.
When I say that I pump soft... I mean that I don't have a total erection, by soft, I mean semi-flaccid with a hint of a chubby. It's best to experience all of the stages of erectile growth as you can in the tube, it is the best for growth.
That said... pumping hard is the ONLY way to gain any extra length when pumping. Since I have the type-2 gene for diabetes, I must be careful not to get too hard during my pump sessions for fear of putting to much pressure on my capillaries and I haven't gained hardly any length in the years that I have been pumping as of a result.
Good luck.
