I think you're going to have a hard time developing a hard break on a peel drop. Every video of peel pitches that I've seen, plus watching several girls throwing peels, all have the action of the ball being a rather symmetrical arc. I have Hillhouse's videos, and his peel (which he strongly promotes as a primary weapon) follows a very constant arcing path from his hand to the catcher. Not to say it isn't effective, but a sharp break it ain't.
I don't have any verification of this, but I think the big leaguers use both peel and roll-over drops in their arsenal, with the roll having more sharp break to it.
Jim