"The first thing you have to understand what is happening with the body before you can make a long term, habit breaking change on the water." - Adam
I certainly see both sides of the situation here. If you are efficiently leading your turns with your CoM with your palm is turned down and it is incredibly awkward for you to turn your palm up, then I wouldn't really suggest turning your palm up. (at least for the time being)
But I have witnessed many of times simply turning their palm up brings a whole bunch of other things into alignment and has significantly, no vastly improved their turns.
Try this little drill. Imagine for a second that you are at 45 off ( yea the rope is going to stop 7.5' inside of the buoy). Since the rope is such a short length you are going to have to be fully extended. Now stand up in your slalom stance in front of a mirror, stand up tall and reach as high as you can so you are fully extended (you are now standing on a vertical plan, but imagine yourself on the water parallel to the water) and start to play with palm up, or palm down. Palm down would be facing away from you and palm up would be with your palm facing towards you. With your palm facing away from you, or "down" you can see this creating some rotation (translates into your CoM falling back, ie not leading through your turn). While with your palm facing towards you or "up" you can see the start of counter rotation (translating to your inside hip coming forward). Obviously this is an extreme example, as I think it is physically impossible for me to get around a buoy at 45 off, but you can start to see the biomechanics of both of these handle placements.
If placing your handle up is a major set back there may be something else going on in the equation. Try getting some video of yourself so you can actually see what is going on on your body, or try visiting a ski school where pros can watch you piece each piece of the puzzle in for you. One week skiing with a pro can help your skiing more than an entire season of chasing buoys.
Adam - Im bottling my Imperial Stout today, so you should stop drinking your PRB crap, hop onto a plane and come check out the SLC. Next on the list is a double IPA. Love beer, love skiing, Love Life - Tom