http://ozreport.com/forum/viewtopic.php?t=10966&start=31

Frame 2 shows the pilot beginning to run. While it is not a fast or jack rabbit start, the relaxed hands allow the arms to lose contact with the downtubes. Arm contact with the downtubes, where the hands are wrapped around the downtubes and the forearms are held firmly against the downtubes allows for continued pitch control of the glider. Once the arms come away from the downtubes the only pivot point would be the contact with the shoulders, which is a bad system because the contact with the shoulders ends as soon as the glider begins to lift. Hands alone have no leverage. It is exactly this image that tells me that a launch is going to go poorly.