ZestKit Tweening Library overwriting tweens

I started using Prime31's awesome tweening lib ZestKit after using GoKit for a while.. It's been working great, but I had always chained tweens or had tweens that didn't overlap. I'm wondering how ZestKit does overwriting, and how I can make sure when I start a new tween that it overwrites one that is already running.

The best example is a simple button that scales up on rollover and scales down on rollout. Since the user can rollover/out before the tween is over, it needs to overwrite/stop the currently running tween. I tried it just with the defaults and it easily breaks and shows the wrong state when you rollover/out quickly.

I remember GoKit had options for overwriting but I don't see it in ZestKit.

thanks! -kc