Take a loot at this video http://www.youtube.com/watch?v=GX47t8IrLq0
The first guy has an eastern grip and he swings open to square or slightly closed. The second guy SW and swings closed -> square
The reality is, that the face angle at impact should be similar between to two grips. So if you are open on your take-back, you need some wrist deviation and pronation to square or slightly close the face at impact. If you pronate on your take-back, then you will open as you swing to contact just as SW players do. You need to analyze your face angle at impact and your height above net. You don't have to put massive amounts of spin on the ball to keep it in. That's just non-sense.