It's more like eight miles between Islip Saddle and Baden-Powell.
I'm not sure I would recommend it as an overnight backpack, as the only water is at Little Jimmy Spring. Even the Islip-Baden-Powell-Islip round trip can easily be done in a day. My wife, who has little hiking experience and only modest conditioning, was able to do it in about 8 hours, including lunch breaks.
"Got tight last night on absinthe and did knife tricks. Great success shooting the knife into the piano. The woodworms are so bad and eat hell out of all furniture that you can always claim the woodworms did it."