I start my boil at 1.5 gals and top off to 5.25 gals.
Most of the time I use up to 1.5 oz of bittering hops and no aroma or flavoring hops. I rarely ever use 2 oz in a batch.
I've been experimenting some lately using only 5 lbs of DME per batch trying to get an enjoyable light ale without it being a diet brew.
Once I used 4 oz, but most of it was for flavor and aroma.