CSS level 1 does mention about the idel body position, but this is more for when riding in a neatral position, not really hanging off. I remember Andy Ibott saying how the ideal position when upright is to just sit back in the seat and then dropp your elbows down and slouch over the tank (almost like you have no spine).
And then for corners as mentioned above (inside elbow/shoulder low, head/spine/bike parallel) etc.
Body position I believe is covered more in CSS 3. I'm due that level next and get the feeling its going to be the most helpful of all the levels for me as my body position I know holds me back and is really pants!
Added: Well what do you know...speak of the devil
[Edited on 11-7-2005 by Harv748]