Chastity and orgasm denial discussion

Hope you can help. I messed up the sizing on my first Jailbird and want to get it right this time! I have the sizing rings which should assist… Regarding the internal diameter of the cock ring: 1.75 (the one I bought initially) allows more than just the tip of a finger to pass through… 1 5/8 feels snug - is that perfect? With a bit of pressure, I can manage into the 1.5 size as well… Should I consider a custom 1 1/6 option? The cage internal diameter: It’s either 1.25 or 1 1/8; the latter fits my shaft snugly but my glans measures closer to 1.25. Is this measurement key - is it better to go tighter? Length-wise, I’m about 6 inches hard and 3 inches soft. There seems to be agreement that smaller is better, but how small is too small? Hopefully, I’ll nail the dimensions. Thanks a lot, simon