Simple way to see how it'll feel on your knees:
Stand with your feet approx 21" apart (centre to centre) or whatever your bindings are centred on. Point your toes directly forward, then try to bend down and twist forward and back. See how it feels on your knees?
Now point your toes roughly 15 degrees out on both feet and try again (11:30 and 12:30 on a clock is 15 degrees +-). See how it feels on your knees? You can try the same thing at different angles, less rear angle, more forward, etc. and it should give you a rough idea of your comfort zone.
SOME people are comfortable at 0/0. I'm not one of them... I'm heavily into freeriding and I still ride -12/+12 or so, because when riding switch and/or doing freestyle tricks in the off-piste I want a symmetrical feeling.