Thanks for the help. A follow-up (procedural) question.
With a 5-gallon brew, I'd boil 2 gallons of water and pour it into the fermenter. Then boil 3 gallons for the wort. Now ... with a half (2.5 gallon) batch, do I just do one boil (2.5 gallon wort)? And will that affect the IBUs (flavors)?