Let me start by saying, "I've never dry hopped before".
My AIPA is about 80% done with attenuation according to the hydrometer. There is still a layer of krausen riding on top of the beer.
Should I wait until the krausen falls? Or should I just drop the pellets in and give it a good stir?
Firestone Walker begins dryhopping when there is about 1P (~4 gravity points) left to go - I'd let it go a little longer before adding, but otherwise you should be fine.