I like nutters for squirrels. Never had one stick in a tree but it will devastate a squirrel. I leave about 1/4" of the tapered shaft sticking out the forward end of the nut then coat with super glue to harden the tip and secure the nut.
I have shot squirrels with judos at close range and the squirrel ran up the tree never to be seen again. I never had luck with rubber blunts.
Manny Pedroski from Hawaii used a big rubber blunt that he castellated the forward end of and had excellent kill power on mongoose. I believe he posted pics of his set up here a few years ago. Do a search.