what do you mean by "covered for the full value" ? How does that help me if buyer claims he didn't get what I sent and Ebay will almost always side with the buyer... There is no real definitive way to prove I sent him the right item...
I believe ebay has a cap on how much they cover.
If you have his signature, and the weight matches what you said it was, IIRC it was mentioned upthread that ebay should side with you.
If you don't want to deal with it, cancel the sale and block him.