First off, you are a jackass if you use piston controls on twins. They're a high-end race and carving binding, they're not meant for 540s and stuff, if you do, they will break. It's not even recommended using 1 piece bindings on twins (it alters the flex of the ski and doesn't let the ski completey flex to the shape of a pipe wall). Many pros use two piece, and it works well. Don't use super-expensive race bindings on twins, its just like using a race ski altogether. Use some inexpensive 2-piece, they're meant for abuse.
Proud member of the Ghetto Park Builders Union local 637