If you are using the Free Auctions to keep your costs down, the above suggestion will not work.
But you can set your Seller Preferences to Block bidders without active Paypal accounts, which has some of the same effect.
I find that if I send a polite Day 3 note asking if the customer needs help with their PP account, that about half the time the buyer will pay up promptly, apologize and leave positive feedback. The others get a Unpaid Item Dispute on Day 4, are never heard of again, can't leave feedback, and go on my Blocked Bidder List.
My entire eBay stock is on Bonanza as well. And I had a sale there just last month. EBay has the eyeballs.