I sold a differential to a member which required modification to achieve his needs. It turned out that what was desired could not be done so I need to refund his money. What is the best way to do it and minimize our paypal fees. Do a refund of the original transaction seems obvious but is that the best way?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.