I haven't used an Snes controller in a long time, but when I did, I held it upside down, with my left hand controlling the buttons. Thumb on X, index/middle/ring on the other 3. If I needed to hit R I used either the base of my thumb or the left pinkie. Right hand thumb rested over the L button, index and middle finger for d-pad control. Ring finger was between start and select and could swap between them pretty easily. Right pinkie was used mainly for support. Left pinkie could also reach over to hit start if I needed to press start+select. But I have fairly big hands so that may not work for everyone.