Adam: The way I picture it is as the "wrapping" wick is actually affixed at the top and bottom of the cathedral fold. I'm fairly certain that this construction method cannot accidentally come undone.
However, I agree with your hypothesis on brightness and burn time. I have been experimenting with various folds (I used to be an origami freak) in order to *increase* surface area for a brighter flame.
I'm not sure I'll ever be as hardcore as you are in your testing methods -- I just stick to different poi types in either hand and compare as I spin them. Not nearly as scientific, but much more fun. Not that science isn't fun, 'cuz I'm a pretty hardcore science geek, too...
-p.