Internal Diameter Advice? (Touching or just barely not touching?)

For open cage designs like mcn's contender, should the internal diameter be chosen to lightly touch the flaccid penis, or should there be a tiny amount of expansion room? My flaccid diameter is 1.22 at the shaft and 1.29 at the largest part of the glans. I'm currently in a Steelheart that's 1 3/8 in diameter, which I chose because I wanted a little bit of breathing room since it's an enclosed design. It's comfy for long term wear, but I have no experience with more open designs, and don't know whether 1.25 or 1.375" will be more comfy.

Thoughts?