Adding Peanut Butter Vodka to Imperial Stout

I am about to transfer my extract kit-made imperial stout to my secondary and want to try something original! I'm fortunate enough to live about 90 minutes from Dogfish Head in Rehoboth Beach DE. I have bottle of the peanut butter vodka they make and thought it would be a nice addition to a stout. Looking for subtle peanut butter flavor but not trying to showcase it. How much should I add to a five gallon batch and is there anything I need to watch out for (alcohol levels w/ yeast for bottling etc.)?

How strong is the PB taste?
You can make you own flavoring extracts by soaking whatever (vanilla, spices, nuts, etc.) in about 4 ounces of vodka for a couple of weeks. Then add the vodka to 5 gallons.

I'm just not sure how much PB taste you'll get, especially in a Imp stout.

It has a pretty strong flavor and if you open the bottle and sniff it you may as well be smelling a bottle of skippy, it's great! Thanks for the tip on other flavors also. If you think the peanut butter flavor will have a lot to compete against in the stout should I up the amount? Is there an upper limit (like a cup) that I should observe? Thanks!

You can flavor to taste-in the bottling bucket.
add a shot or two with the priming sugar, and rack the beer into the bucket.
Give it a taste and if you need more flavor, add a shot or two and gently stir it in.
Repeat as needed.

As far as how much is too much, I'm not sure.
I'd think with a cup, you should be fine in 5 gallons.

To be safe, add a cup, and bottle half (24 bottles).
Then if you want more flavor, add half a cup to the rest.
(or 4 ozs, bottle two sixes, add 4 more ozs, bottle the remaining two sixes).
Mark the bottles, so if the last ones bottled are flat and taste like vodka, you'll know next time.