Advice on internal cage width

For cage designs with open fronts, such as MCN’s Contender, should the internal diameter be selected to just barely make contact with a flaccid penis, or is it better to allow a small amount of space? My shaft measures 1.22 inches in width and my glans reaches about 1.29 at its widest point. I am currently wearing a Steelheart with a 1 3/8 inch diameter; I picked that size because the enclosed design needed some breathing room. It wears comfortably for extended periods, but since I haven’t tried more open styles before, I’m unsure if going with 1.25 or sticking to 1.375 inches will feel better.

What do you think?