This topic probably belongs in the PFD section but this looks like a "dead thread", so... here goes..Kayak instructors always stress the proper use and fit of a PFD. The adjusting straps should be drawn tight enough around the body to keep it around the waist and chest. When some paddlers wet exit, their PFD winds up over their ears. If they were to raise their arms as in the "Help!!!" manouver, they could slide out of it. I hate to say it, but this is a problem with heavy (read "chubby" paddlers. You want the PDF to give bouyancy to the middle of your body, not to the head and the top of the shoulders. How can a heavy paddler keep the PDF were it was designed to be?? (I know... lose weight). This is complicated by presence of the kayak skirt. Children's PDF's used to have a crotch strap. How can we re-engineer the PDF to be more secure and more functional??

Just like you said; add a crotch strap.

A while back we presented this question to several life jacket manufacturers in our SK e-newsletter. You can read their comments in our e-newsletter archives at http://www.seakayakermag.com/2008/08e-newsletters/June/pdf-questions.htm