i recently bought an Ergobound and a couple of your plain round Base Rings, in two sizes (42mm & 46mm). The smaller ring was too small for me, but the bigger feels great. i'm happy with it and so is my Keyholder. Security is not His top concern: He extends me a lot of trust, which i do not abuse. But there is a security weakness that i thought i should mention: my balls escape easily from the bigger ring. Dexter here is always jumping out of his corral. The upward tilt of the locking stud means the ring-tube gap gets wider and wider as the ring gets bigger. ideally, i'd love to have the same cross-sectional area as my 46mm ring, but with a tighter gap somehow.
Again, this isn't a call to action or a request for anything -- i just thought you would appreciate feedback on how your design is working in the field. If interested, you can see me wearing on my KH's blog at master3by3's tumblr. Thanks for making this design available.