I have a Retina IIIc and a Retina IIc. I just received a Kodak Series 6 adapter ring (31.5mm/1.25"). It slips on the lenses of my Retinas closely but does not snug up. Sothe adapter ring falls off the lens. Is it common to get the pliers and slightly bend a few of the ring prongs so that the ring will secure itself on the camera lenses? OR did I buy the wrong size? Thanks.