Thanks for the information Rob, and others. Very interesting stuff. I guess, like many design problems, there's a balance to be struck. Under 'normal' loading, you want sufficient pull force to ensure that the white loop has sufficent grip on the lolon cable so that the risers don't release if the cut-away handle is floating. On the other hand, under 'abnormal' conditions, you still want to have enough mechanical advantage to allow a release of the risers.
Whatever way you slice it up, when you line up a three ring release with the Capewell system (which I did), the three ring system makes me feel warm and fuzzy on the inside, whereas the Capewell system looks like a bad day out.