The mash wort at 170f decreases in volume by 5% by the time it cools enough for pitching. I use that to calculate the mash water amounts.
So a 5 degree difference will create just a bit of volume shrinkage.
BEER: The Cause and Solution to all Life's Problems
Aging: Ugly Monk Belgium Abbey
Drinking: Heavenly Honey Wheat,Chocolate Stout, London Porter, Big Fat Fatty's Oatmeal Stout, Pete's Porter, California Not So Common, Ugly Monk Belgium Abbey, Maple Brown
Upcoming Brew: Bass Clone, Fosters (a light drink for those who think beer has to be light).