So my Chinook SmaSH APA (OG 1.059) had a really crummy fermentation using 1056. This pitch was the first time I built up from a slant and I don’t think I let each step go long enough. It took forever to start (almost 24 hours for visible activity) and over 3 weeks to appear finished. Not surprisingly, it under-attenuated by about 3 points (1.017 instead of 1.014). This doesn’t seem like much but I can taste that sweetness that seems out of place. Here’s the kicker, this beer is supposed to be one of the kegs for a Halloween party SWMBO is throwing. Even though nobody could probably tell the flaw, I’m the type of brewer who wouldn’t want to serve it as is because I know the flaw. So given the options, what would you do?
Not likely that pitching more yeast is going to knock off three points, but if you haven’t already tried it, you could warm the beer into the 70s and then rouse the yeast once a day for a couple of days and see if you can get one last gasp out of it to finish this off. If you’ve already done this, you could aggressively dryhop, like 2-3 oz, which will add a little bitterness along with a LOT of hop character to balance it out a little. Or you could just go with it as-is and know that you’re the only one who is going to notice anything “wrong” with the beer. 
Buy some “yeast energizer”. It works wonders, really it does. Not quite the same as “yeast nutrient”, but in a pinch you could give that a try as well.
You are probably 100% correct in your assumption that no one will notice except you. They will all think that it is great beer and it probably is. As an alternative if you like you could just ship it to me. I love beer that finishes at 1.016. Just trying to help a brother out.
