If you've got a fairly loose sack like i do, it's not that difficult, And yes, the tension on the vas deferens does seem to amplify things, but most of my vids are after some significant edging which obviously makes things explosive ;>)
I don't think I would enjoy working the rings on my sack.I put a pound and a half stainless weight on my balls in less than a minute,and wear it 24/7. I can't argue with your truly powerful cumshot stretching definitely makes mine last an abnormally long time as well....when you think it is over,guess what? It is FAR from over,LOL!
I hope you find it inspirational...
And yes, the tension on the vas deferens does seem to amplify things, but most of my vids are after some significant edging which obviously makes things explosive ;>)