I've done an all-grain stout. Pale malt, flaked barley and roast barley (66%, 20%, 10%)
OG 1.042 mashed around 68°c
So probably won't finish real low.
But i like my beers nearly 6% alc.
If i add 1kg dex (or 500 dex 500 ldm) will it ruin it? Was going for a guinnesss clone and have 800ml...