I am planning to do an Imperial Russian Stout next weekend which will have an OG of 1.094. I usually double batch sparge which works out well and I typically add close to 3 gallons on each sparge for my normal beers. This one shows I will use only 2 gallons per sparge since I'm adding so much on mash-in. With about 17lbs of grain (4 gallon batch), that seems like a pretty small amount of water to add in order to get an effective double sparge. Should I just do a single sparge with 4 gallons instead or would 2 gallons be sufficient/effective?? This is my first high gravity brew....thanks!