If the buyer is not happy, there is a fair chance you will hear from them. If not, then assume they're happy. An email from them fits your requirements, but you said you wanted feedback.
I remember trying to get those magic feedback levels. Buy some C&S satchels if you need that 10.
I run about 75% feedback, which means 25% don't bother, even though eBay send them a reminder after about a month.
