Re: Rod Grip: Thumb or Index Finger?
For myself it depends on what I'm fishing with. If I'm using a lighter rod and smaller flies (dries or nymphs) I cast with my index finger on top of the grip. For heavier rods, bigger flies, or even in windier conditions I find that I place my thumb on top more often.
My mentor always preached that the thumb needed to be on top, but I never was a very good Grasshopper.
*Comments posted above are only my opinion. I may be right....eh, I'm probably wrong. Take 'em for what they're worth.*