I've decided to try my hand at brewing 7.5 gallon batches and kegging in the new slim quarter kegs. However I obviously cannot fill a 7.9 gallon primary with 7.5 gallons of wort and not expect something to blow up or at the very least have half my yeast go through the blow-off tube.
How much headspace would you recommend in the 7.9 gallon fermenter? I was thinking about brewing 6 gallons to a higher OG and adding a gallon of water when I keg. Thoughts?