Therapy Game Adjustment Features

I am currently working on the following adjustment features for my therapy games:  centering the game according to the user's current position, adjusting the on screen range according to the user's arm length, and smoothing the kinect movements to reduce jitter.  My therapy games (Alien Robot vs UFOs and Painting the Roses Red) feature right and left hand tracking.  I am working on centering the user's movements to their Center Shoulder joint (a joint defined by the Kinect as a point between the right and left shoulders).  This adjustment centers the user even if they are not perfectly centered according to the kinect's camera view.  I am also working on adjusting the user's on-screen range according to the length of their arm (measured by the user's respective Shoulder and Hand joint data).  This should adjust the game for differently sized users, and should allow the user to reach to the edges of the screen without disappearing off the edges of the screen.  Lastly, I am working on reducing jitter of the on-screen object that is tracking with the user's hand.  I have tried using a weighted average, and am now trying to use a moving average.  I am trying to adjust how many data points are needed to calculate the average for optimum results.  The more data points, the smoother the result, but factoring in too many data points at a time may result in on-screen latency (delay in movement of the Looking Glass object).  I am making progress on these three adjustment factors, and hope to have them all perfected soon.