The best is to use FRESH peel, soaked in vodka for a few hours or overnight, then add just the flavored vodka on bottling day after fermentation is complete. So if you want to try that, you've still got time to pick up some fresh fruit.
Otherwise, with the dried peels, I would figure about 5 minutes in the boil, or at flameout, would give just a bit of flavor, and a slight bitterness as well.
Cheers and hope you like the results. Please share when it's done.