Hey guys. Currently i having mx80 (3ug2) and kason f9. I am liking the feeling the mx80 which give directness and solid feel. I can out the power during the first few games, with smashes strong. But after few games or after few big smashes, will get easy. So is it about my stamina or? PS: No pains on my muscles so far. Using kason f9 have different feel, it is much more save energy. With the small effort, get big power. But sometimes, it is difficult to control the power with the flexible racket. Any recommendation can help? Thanks pro for giving advices.