Do you realise that COD is going to cost you several times what the buyer paid in the first place?

In most cases I would never choose to be out of pocket one cent just to influence a buyer's decision on feedback however in this case I would consider myself partly responsible, when the buyer asked for a different size, between two of the sizes you sell, I would have sent the exact measurement before posting it off to make sure it was OK. If I hadn't done that then for such a small amount I would probably have just refunded and told them to give it away.

If I had confirmed the exact measurement before sending then I would just stick to my guns and say it would be refunded on return and they could leave any feedback they wanted.