I try to brew mainly with whole hops, as pellets tend to clog up my sure screen. As such, If I used more than a half pound of hops, I would be concerned about how much wort is absorbed by the hops.
Last week I brewed a 10 gallon batch of Belgian blond with 8.5 ounces of hops, all leaf. I stopped the boil with 11 gallons of wort in the kettle, but only managed to collect 9 gallons into my two fermentors. I left the kettle to clean the next day. When I went to clean it, it felt somewhat heavy....so I opened the drain valce, and collected 1.5 gallons more wort! Evidently that had drained from the pile of spent hops sitting on top of my false bottom overnight. I re-heated that wort, chilled it, and topped off my fermentors.