I think I figured out how much water I'll need so that I end up with 5 gallons in the fermenter. Please have a look at my math and correct if necessary (go ahead, I can take it)
I'm starting with 10.13 lbs. of grain.
I'm figuring 2 quarts per pound of grain in mash for a total of approx. 5 gallons.
I'm figuring .12 gallons of loss to grain absorption for a total of approx. 1.2 gallons.
Equipment dead space loss = approx. 1/2 gallon.
Evaporation loss due to boiling = 1.5 gallons.
Total water needed = 8.2 gallons.