I have big knuckles so rings can be a problem.
Band-style rings are ok but solitaire-type rings will keep rolling on my finger and the solitaire will end up facing downwards!
I'm a size 6 (52 in French sizing) for my ring finger and a size 7.5 (size 56 or 57, depending on the ring style) for my middle finger.
I like wearing rings on my middle finger but it's sometimes hard to find the ring I want in a larger size.
Have you thought about having sizing beads put into the inside of your rings? I wear a 5.5 because of my nuckle.. The beads really prevent my ring from turning or spinning