Power Stone code looked messy, also tricky to modify if you wanted a different curve or speed.
So I made it smoother.
Recolored stones included to show what kind of stuff you can do. Red is the one closest to current power stone.
(http://i.imgur.com/G1wJgG4.png)
http://www.best-ever.org/download?file=powerstonerecode.pk3