[Bigwill]

Watching the US open last weekend, there was some closeup of his swing. It looks like he had interlocking grip. I have it taped and could review again. Are you implying he used a reverse overlap?

No, it's an interlock. It's just that his left index finger kind of hangs free, almost like he's pointing it, rather than being curled around the right pinky. I do it this way when I interlock; it seems to help keep excess tension out of the left forearm for me.