To Fiveniner: you can buy directly from Softie a square emergency
parachute.

To 66: it is called weathervaning...go and make a jump, don't release
your brakes and see what the canopy will do. Especially the big ones
like Raven IV.

To Eric Greenwell: no it doesn't work like that. Round/conical will
descent at that rate no matter what. There will be a small difference
in descent rate between suspended loads (heavy pilot versus light
pilot) but not a really significant number. If you would like I can
swing by the airport and drop you a book with explanations about
parachute desingns. I don't want to type the explanation because would
be to lenghty.