So I have done 10 ag batches so far and have messed with initial mash water added. I typically have ~17lbs of grain and use the Coleman extreme 70ct cooler. My first couple of mash's I used the recommended 1.25/1.3qt per lb. There was a lot of dead space in the tun so the last few times I have used half my total water needed pre boil then added the rest for the sparge after draining into boil kettle. So usually ~8 gallons mash then 8 gallons for the sparge gets me just over 14 gallons in the kettle.
Does anyone else use more water for the mash in step? I read this http://hbd.org/cascade/dennybrew/
but would think that the way I am doing it would lead to a lower efficiency but I am consistently in the 80-85% range now that I dialed in my crush.