When I list a multitude of items I specify $2.50 shipping no matter how many items are won during the listying period. So a buyer would pay $2.50 for one item, or two or more items. You could ship 3-4 chips for the $2.50 cost and if a buyer has more then I figure it's a win because I sell more items and they get a shipping bargain.

On low priced chips I rely on the USPS tracking number to show delivery. If it's a high priced chip then pay the insurance for your own piece of mind.

Free shipping is a penalty to someone who buys multiple items shipped at same time as the seller has already bult the shipping into the price asked. Of course as soon as the bids go over the minimum bid then this theory is out the door as now the buyer has figured the shipping into his final bid.