Adding cacao/coffee tincture to my stout??

I'd like to beef up the chocolate,coffee,caramel flavors/aromas in my stout so I was thinking of using some cacao nibs,caramel flavored coffee and vodka to make tinctures as opposed to using more sugars or syrups,the flavors of which would most likely be lost during fermentation.

I've searched the boards for this but haven't found a definitive answer...I was wondering if anyone's added a coffee or cacao nib tincture to their stout that could give me some insight into the process,suggested ratios to use,etc.?

Any help with this would be much appreciated,thanks in advance!!

**obligatory newbie bump**

I know other people have experimented with this...I'm really just looking for amounts to use,whole beans as opposed to ground,etc.