Originally Posted by bendport
In my experience, having a cupped wrist at the top would typically be caused by a weak grip or a grip where the left thumb position was too pinched backwards where as a bowed left wrist at the top would be caused by a strong grip or a grip with a long left thumb. Are you fanning the club open on your takeaway as this can often lead to a cupped position at the top?
That hasn't been my experience.
I've seen the opposite more, as a strong grip that's bowed will be even more shut at the top of the backswing. A strong grip is naturally more cupped than arched at setup as well.
I encourage individual diagnoses on these types of things. Some players feel the grip is strong and the face a little "shut" so they cup their wrist to help keep the face open a bit (Fred Couples - strong grip, cupped at impact and top of the backswing), others let it arch (Dustin Johnson, not that his grip is particularly strong).