Flour Sack Animation

I don't know a whole lots about animation, but from the little I have an idea of I can really only say two things: The animation itself looks very smooth, which is good. But the flour sack doesn't appear to have any sort of weight to it. There's no squash and stretch other than on the one 'foot' when it takes off to emphasize the movement, and especially when it lands that would add quite a bit to the whole thing. So while it looks like a flour sack, it doesn't have the weight of a flour sack and so it appears a bit off.