Shifting one's rear on the seat

[Rockitman]

I am practicing Chopin's Etude op10 #3 in Emajor and have it all mastered except for the tricky part at measure 47 (con bravura).  I find it difficult to hit these notes correctly with the left hand as he is playing over to the rightside of the keyboard.  The reaching just does not lend itself to comfortable playing here.  Do you find yourself shifting your rearend to the right a bit on the bench when you find yourself playing a passage  where both hands are playing in the upper registers?  Or is this a bad habit?
I'm playing on a stool right now so I cannot even try this but if I had a bench, I could see myself shifting over a bit to get more comfortable with this part.  

[super_ardua]

Don't shift.  Your playing is broken while you are shifing place.

[squinchy]

I admit it-I shift. Probably from my unwise practice habits-I'd always separate the first note of that section from the last note of the chord before. Therefore, I would have ample time to shift. Now that I know the piece relatively well, I've diminished it to more of a torso-lean. It moves your hands over without the bottom-bump.

[Brian Healey]

I'm not familiar with that piece off the top of my head, but I agree with the previous poster that a torso lean is the way to go. I was always taught that you want your chest to be between your two hands as much as possible. When you play at the extreme ends of the keyboard with both hands, shift your body weight to the side you're playing on, but also INTO the keyboard. For instance, when playing in the high register, most or all of your body weight will be on the right butt-cheek, and your torso will be closer to the keys. Basically, your body is moving in half a semi-circle, if that makes sense. That's what I would suggest, without looking at the piece.