Don't waste your time with David to scan people. I've tried. If you make a small calib panel and try to scan outside of it, you lose the optics. It bends and is not worth aligning.
Scanning people with Kinect, etc works better, but you need a very good GPU (gaming card). The only way I know to get a quick human scan is a system like this...
http://ir-ltd.net/Very expensive. Photogrammetry, methinks. I would love to know if anybody has had experience using 123d catch to get a good person scan by using multiple cams at once.