Hmm this video shows them getting close to the edge. I expect I might be able to do it if I had a pillar drill, but I really don't want to keep buying laser cut rings only to destroy them. Maybe I'd be better off using aluminium?.. I could do with some scraps of acrylic and polycarbonate and a pillar drill; I'd soon find out if it could be done. I just tried hand drilling a 3.4mm thick bit of either acrylic or polycarbonate (not sure what it is), with a 1.4mm drill bit. It didn't crack but was pretty dodgy; wouldn't take much at all to mess it up. I need to make the rings thicker, or use aluminium I think.