Chastity device discussions and reviews discussion

I’ve spent a few days browsing and reading through the forum on this topic, yet I still haven’t cleared up my confusion. My measurements are 70 mm in length with a soft diameter of 29 mm. The advice seems to suggest that it’s better to choose a size slightly smaller or based directly on the flaccid measurement. Since my penis measures 70 mm when flaccid, I figure the cage length should fall somewhere between 65 mm and 70 mm for an optimal fit. However, would 75 mm still work even though my flaccid length is only 70 mm? Would that extra 5 mm of space cause any issues? (I’m wondering if those additional 5 mm might lead to more painful erections compared to a tighter 70 mm cage, which I believe fits well.) I feel the cage diameter should be suitable between 30 and 32 mm, perhaps up to 35 mm at most.