I am planning on adding some sugar free blackberry syrup to a Robust Porter recipe from Brewing Classic Styles. I am using this syrup, http://www.blackberrypatch.com/sugar-added-whole-blackberry-syrup-p-333.html. I am thinking about adding it to the secondary and or possibly at bottling. This is going to be an experimental 2.5 gal batch. Any one else ever use a sugar free flavored syrup in a brew?