well, keep in mind that flat, unfinished beers often don't taste quite like the final product. carbonation might literally bring those flavors out that you can't notice in a hydro sample. also, drying out a few more points might accentuate those notes as well.
I usually hit my wits pretty hard with zest during the finishing of the boil so I don't add anything post boil anymore, but a few years back I would put some orange zest in after primary had slowed down. but I put the zest in without doing anything but giving the fruit a good wash and rinse before zesting
- I know, pretty blasphemous, but I figured not much would occur now that there was a low pH and alcohol present in the beer. It always worked out great, but I wouldn't necessarily recommend it.
anyhow, tincture as tschmidlin described is a great path as well.