A GREAT way to fix that would be to add some concentrated coffee. Brew up 4 cups of coffee using about 2-3X the normal amount of coffee grains (or 2-4 expresso shots if you have an expresso maker), cool it down to about the same temp as the beer, and dump that puppy in. It would be best to add it at bottling/kegging time.
Coffee is a great addition to a porter or stout style and will cut that coconut nicely. I used this same method to save a porter I added too much vanilla to, and it turned the beer from undrinkable into a really really good beer.