if the non-payer doesn't respond too the dispute you open within 7 days, then they can't leave negative feedback. You should leave them negative feedback though to warn other people, otherwise the whole system becomes pointless. if you get one back, then respond factually saying something like "Retaliatory feedback. Non-paying bidder, fees reclaimed." or something similar. Any sensible ebayer will not be bothered about that.
If you want to be sneaky avoid leaving the negative feedback until 89 days after the auction finished and they may well not notice and they can't leave you any feedback after 90 days anyway.
If your second highest bidder doesn't want the item, you can relist it for free anyway
Don't leave anything insulting though