I know this level. I was borderline 1st/2nd division and stuck on that for a long time (occupied with other 'life' things). I agree with Matt it is practice that is needed. A high jumpsmash is not really needed for doubles at this level. What are you trying to achieve with a jumpsmash? If you are looking for power, it's not really going to make much of a difference. I think you need to re-look at technique and body position for overhead action. Are people returning your smashes easily in doubles? Despite you putting in a huge amount of effort in your smash action, is your smash just the same as the 12 year old on the adjacent court? Is there something in your technique that makes it easy to predict the pathway? (some people's clears and dropshots actions are different to a smash). Are the smashes slightly sliced inadvertently thus losing power? Are the direction of the smashes played in such a way to be effective? You wouldn't believe how many people try to cross court smash in doubles hoping to 'surprise the opponents'. Are you only smashing with your arm and not rotating your hips, body and shoulder? From my own personal experience, learning one new shot won't make a big difference. I decided to relearn everything from the ground up. For example, started off with footwork. Then we progressed on to straight smash - two steps forward and netkill - sidestep backwards, smash, two steps forward and netkill. Did quite a lot of this as the smash against a regular singles player defender is less so an outright winner. Also did the routine diagonal cross court as well, with the addition of a skip step after the smash and before the two steps. So, yes, I played a lot of smashes in training and not a lot of deception! Once I got the hang of that, we worked on defence, timing of bounce, body position and movement for optimal speed. So, it fits exactly matt's principles of getting fit, improving speed, improving all round technique and a lot of practice.