Padlock vs screw I think is more personal preference...
For sizing, the way I understand it you have the best tool with having a CB6k already. You can base all the measurements off that if you have a comfortable fit. Since it sounds like you don't I would think you first need to figure THAT out. Is the ring too tight? Cage too small? Etc.
I just ordered the sizing rings from MM myself. A lot of people say that is the way to go for sizing if your cbxxx isn't right. I am also lookin at the QK but can't order till income tax return. I'm going with security screw due to not likening the padlock thing (just my prefrance). Plus you can pick a padlock pretty easy if you want and they say screw is easier to hide. True no device is ex cape proof but it won't do much good to pull it off and it still dangle around my balls. Any ways read some others post that advise leaving room not much for eretions. And extra room if not cut. Not sure why your 6k hurst but if it is from the ball stretching a metal device won't fix that. If you have a too small base ring or wrong spacer that can cause extreme pain as well. Good luck and let us know how it fits when it comes in.
Markbentorah wrote:Slipping your bits (Balls first and then Cock – for me) through a solid ring was different than the size I used on the CB which you basically build around your bits. With a bit of technique (but not much) I settled on the ring size, which was smaller than the CB ring size.
While I don't own a metal device (yet) I still believe that that is a good starting place for sizing based on what I've read.
That said, I will agree that it is a bit different. I could NEVER get the smallest CB ring built around my bits, but with very little work I can slip into a 1.5" solid metal ring I have. I think it's too tight for use with a belt though, but it's still interesting how the solid design can change things a little.