Put your racquet on the ground (preferably a hard court or on concrete floor) and lightly put your foot on the top of the handle area so it doesn't move. Then hold a tennis ball above the strings from about your belly button and drop it onto the strings, and watch it bounce. You can drop it on certain parts of the stringbed to easily see where your racquet has dead spots, or the sweetpot. If i divide the head into thirds, my Yonex RD Ti 50 has dead spots in the bottom 1/3and on the outer areas, but has a suprisingly large sweetspot from just under half -way to just under the top of the frame. But the best area is definitely from dead centre to just above dead centre. Make sense? Also, if you do it barefoot, your foot can give you great feedback, i found when the ball hits the sweetspot, your foot feels nothing, but when it hits a deadspot, you can feel the jarring in your foot. Imagine what it must do to our arms!! Anyway, see for yourself!