need advice from karma police

[The Radium King]

hi all. recently bought some parts on ebay. parts turned out to be misrepresented by vendor. asked vendor for refund but he delayed. raised dispute on ebay and he promised refund in return for me shipping parts back to him. i did so at my expense with a promise that he'd refund this cost as well. he then delayed the refund to the 1 month ebay dispute limit, so i escalated the claim. he has now refunded me the cost of the items, and the cost that was paid to ship them to me. he has not refunded the cost for me to ship them back ($80) as this cost was not part of the ebay transaction. he now says that he will refund me this cost as promised, provided i leave him positive feedback.

what to do? leave the feedback and hope he refunds me? leave negative and eat the $80? leave positive feedback but slam him on the boards? i stuggle with my conscience.