CB Range discussion

I’m trying to figure out which CB suits my penis size best. My length is around 17 cm, and I have a fairly large scrotum (currently using the biggest ring with the CB3000). I could also go for the 4.5cm ring, but during an erection (my penis attempts to rise;)), the CB3000 feels a bit tight. This causes some pain near the bottom of my scrotum. Should I switch to a larger model like the 6000 or Curve, or stay with the CB3000 and its biggest ring? I’m asking because there’s already a crack on one side of the locking area in my current CB3000, running from one pin toward the center hole. Once it gives way completely, I’ll decide whether to buy another CB3000 or upgrade…