I wouldnt give him his money back at all, and take the seats back. Wait until he give you the rest for shipping.

I would have never left the seats to be COD to him to begin with. Because anyone would have refused to pay for the COD especially since it was more.

He has no arguement. He has waited so long to reply and send you money and so forth. Let him post you negative feedback, it dont mean shit on the first one. Especially if you have many more positives.