I normally use the continental grip for both my flat serve and my kick serve. Lately I noticed that I have been double faulting more than I should be. I switched my grip on the second serve to an eastern backhand grip so that I could hit with more spin on the kick serve. I noticed very few double faults, but sometimes the ball would land short in the service box and my opponent would attack it. I have used the eastern backhand grip to learn the kick serve as advised by my first coach. I switched coaches and he told me to use continental. Now I have a new coach and he hasn't talked about my serving grips at all. I have had ample experience with both the continental and eastern backhand grips for the kick serve. Would you recommend that I learn how to double fault less with the continental grip or continue to use and try to gain depth and height with the eastern backhand grip?