If I start the piece from a neutral position in relation to my left hand I find that when I get to the arpeggios in measure 107 I can't comfortably reach them with my right hand. If I start the piece seated further to the left then parts of the beginning movement place uncomfortable stress on my left wrist in certain places (measure 3 for example). How do people deal with staying neutral with the wrist when the piece moves all over the keyboard like this?
Sitting so that your body is (more or less) centered on the keyboard is best. I cheat very slightly to the right, because that's comfortable for me.
To play the passage in mm. 107-108, I lean out quite far to the left (lean, but not shift where I'm seated) and step my left foot out to help keep my balance. I keep my body square to the keyboard (no twisting), so stepping out is essential for me.
Hand position #1
My right-hand thumb is placed near the leading edge of the key, while my right-hand pinky is closer to the fall board. This allows me to keep my arm/wrist position fairly straight. It's also important to let the hand (the thumb, in particular) contract as the arpeggio is played — don't try to keep all the fingers on their respective notes.
Another option is to play the initial right-hand
Gs with the thumb of the left hand. That allows the right hand to be in a more relaxed position to play the other notes of the arpeggio. Note also the wrist is a bit straighter in this position.
Hand position #2
A variation on the above (playing the
G octave with the left hand, and the remaining three arpeggio notes with the right) is to change the right-hand fingering from
1 2 5 to
2 3 5. This allows for a hand position that stays on the wide part of the white keys, rather than placing the fingers toward the fall board, between the black and white keys. It also allows for the straightest arm/wrist alignment.