I'd just refrain from leaving feedback if you care about getting a neg in return. There's nothing that you can do to stop it, unless you want to try and get him NARUd. File an Unpaid Item Dispute and if he doesn't respond in 7 days, get your fees returned, and he'll get a strike. Hopefully that will be his third. Drop him a negative around the same time, and generally eBay will get him NARUd within several hours. If he negs you before they NARU him, you can just have eBay remove the neg anyway because NARUd members aren't allowed to leave feedback. But like I said, just leave NO feedback if you don't want to risk it because there's nothing you can do.