in the actual keyboard i find the nubs too far from the thumbs (especially for little hands).
the hand position is not comfortable if you want to play with nubs a long time.
so i wonder if this layout could improve the comfort?
My hands are small and personally I have no problems with using the nubs. I would suggest holding your Pandora for a long time in the position that your layout would suggest - I suspect it would cause a great deal of pain.
I don't suppose you happen to have a Nintendo DS to hand, do you? If you do, try holding it and positioning your thumbs close to the middle of the top of the touch-screen. Prior to receiving mine, this is how I checked to see if I would find it comfortable to use.