Chastity device discussions and reviews discussion

I’m thinking about purchasing a chastity belt. It would be the first one I’ve owned. Right now, I haven’t made up my mind between choosing the CB-6000 or the BON4m; that’s a separate research project of mine. The real question for this thread is SIZE. My penis measures roughly 5 cm when completely flaccid, which seems like it should slide easily into an S size model since both devices have internal widths slightly over 6 cm. But I keep asking myself: what am I trying to achieve by wearing a chastity belt? Do I want total prevention of erections, as happens with the smaller cage where my penis begins to swell and hits the walls fairly quickly? Or do I want that crushing sensation and that annoying urge to masturbate when I’m right on the verge of going stone hard? I want maximum punishment. The S size feels like a logical choice for this goal, but since my erect length is about 16-17 cm, an S cage would only allow me to use one-third of my potential girth/length. Wouldn’t it be more punishing if I felt almost ready to release but couldn’t? Is the smaller fit enough?