I put a Joe flacco lot on ebay last week in a 1 day auction and posted payment due in 3 days as i had a couple big bills going out and needed a little pocket cash (gas,lunch at work,so on so on),so 5 days after the buyer won i emailed and asked for payment status,to which he replied "sorry,my paypal is tied up by someone who claims they did not recieve their item,thanks for your patience.Ill let you know when i can pay for item".Today is 7 days so i emailed and said i was relisting.I checked his current items for sale and none current or ended in the last 10 days accept paypal as payment which tells me he did not have paypal when he bid and won my paypal only auction.I didnt want to screw him over,but didnt want to wait a month for 20 bucks either.Sorry for the long post.

if he doesnt abide by your terms, it is more than fair to relist the auction- thats one of my major pet peeves with ebay, people who bid and dont follow the sellers instructions, so as long as you were very clear in your auction, and have tried to communicate with the buyer, like it seems you have, i say file unpaying bidder notice, relist, and then appeal the negative that he will probably leave you as a seller...
Ed

if he doesnt abide by your terms, it is more than fair to relist the auction- thats one of my major pet peeves with ebay, people who bid and dont follow the sellers instructions, so as long as you were very clear in your auction, and have tried to communicate with the buyer, like it seems you have, i say file unpaying bidder notice, relist, and then appeal the negative that he will probably leave you as a seller...
Ed

If he doesn't respond to the Unpaid bidder notice properly, then you don't have to worry about the negative feedback, because he won't be able to leave it. Or if he does leave it, you can have it removed.