in wakeboardmagazine kyle schmitd says about 9 degrees is the most common stance in wakeboarding with feet spaced a little more than shoulder width apart for stability side to side. but everyones leg design is a little different, so it varies. your feet should be centered on the board, so switch position is a mirror image of regular position. to figure out your position jump off your bed and dont look at your feet, the position you land in is how your wakeboard stance should be.
another thing he says about angles and the impact on your knees "turning your stance to far outward, or ducked, forces the knees to buckle inwards, increasing the cance of MCL and ACL injuries. Not turning the stance outward enough puts stress on the outside of the knee and its ligaments."
i figured i might add this so you can have a little food for you brain. im just posting what i read in wakeboard mags issue for august 2005. personally i rock some hybrid zeus bindings and i've always rode ducked out one notch and at the furthest inserts. so if i stick my bindings on my board faces the toe edge completely perpindicular and move them one hole ducked out. thats where i ride, and i believe thats about 9 degrees. its worked for me for about 5 years so i'll keep doing it.