You could try something like this. It should work pretty will with Dan Ebbert’s bounce expression:
var influence = 450; //How much do you want to influence the rotation;
var squahLimit = 200; // What’s the maximum allowed rotation;
//var newSquash = transform.scale + transform.position.velocityAtTime(time)/(10000/influence);
var newSquash = transform.scale + [transform.position.velocityAtTime(time)[0]/(10000/influence),transform.position.velocityAtTime(time)[1]/(10000/influence)];
if (newSquash > squahLimit) newSquash = squahLimit
else if (newSquash < squahLimit*-1) newSquash = squahLimit*-1;
transform.scale + newSquash - [100,100]