Well, there's really no such thing as "no returns" on eBay.  Any buyer can return an item with a tracking number after putting a dispute with Paypal who will freeze your funds until the buyer proves you received the item back.  As a power seller, I always accept returns and why not?  What have you got to lose?  You're risking negative feedback and your eBay reputation.  The buyers have the upper hand becasue eBay says they do.  Didn't used to be that way, but eBay doesn't care much about their sellers.  So, let the guy return it "in the condition in which it was sent and received".  I would send him a different sized shirt after you receive the shirt he bid on whether it's flawed or not.