Ditto on Sli and Hillman. I haven't spent a peaceful night at Long Lake except for Catlin Bay, because The Plumleys L/T's always seem to have Scouts or boaters there, so I move on. Another time, some guys were shooting a shotgun at Kelleys Point, so I moved on.
While the closest Cold River L/T's are only about 4 Miles from Plumleys, I did find an small outboard motor leaning against one of the Lean-to's about 15 years ago. Later that evening I found out that some guys motored their rowboat to Plumleys and chained it to a tree and backpacked the outboard motor to CR L/T's so it wouldn't be stolen....
Also, Shattuck's Clearing is a wonderful and slightly closer spot to camp, but with such beautiful L/T's only 1/2 mile away, it is hard to deprive oneself of the sun coming up over the Cold River and lighting up your lean-to in mid-late summer.
But definitely, I would at least bring a tarpand some netting.