I just started taking lessons from my friend, he's not a well established tennis pro, but I feel that he helps my game more than any other person I've taken lesson from. He feels that I should switch to an eastern grip from my current semi-western grip. He says that using an eastern grip gives me easier power and exerts less energey. I plan on taking four lessons a week until the end of december. Would not changing my grip effect my lesson in a negative way? I'm at a 4.0 level and want to basically adapt my game to be similar to my coaches, does this mean it's necessary to change my grip to get the most benefit from his lessons? I've experimented with using an eastern grip and it doesn't feel comfortable. I'm not sure how long it would take for me to be comfortable using an eastern grip but do you guys think it would pay off?