I'm on my third batch of AG BIAB brewing and I had an unexpected 85% efficiency. I had been doing one-gallon batches, but this time I had enough grain and hops to make a 1.5-gallon batch. On bottling-day I tasted the beer and thought I had some bug get in and I had made a sour - the taste was sour-sweet, green, and not really good. After reading all these posts about how bad your beer tastes and 'just give it time,' I let it go. Two weeks later it was somewhat more mellow, but still had a really sweet taste to it and a bit of a bad aftertaste. Three weeks now and the bad aftertaste is mostly gone, but the sweetness is still there. I used beer calculus (beercalculus.hopville.com) and adjusted the efficiency from the default 75% to my 85%. It took my recipe from a solid APA to an under-hopped, yellow, malty-sweet accident (which is fairly accurate to what I now have). I'm not too picky so its still drink-able, but I'm wondering what I can do in the future...
I know I can adjust for next time, but what can you do on your brew-day to adjust for an unexpectedly high efficiency without sacrificing too much of your beer's flavor?