Spiral or a 6-fletch with lots of helical.

Around here at least, a flu-flu is useless on squirrels and even rabbits (which are, IMO, slower than squirrels). They will dodge them--too much noise and too slow. If you are going to shoot at squirrels in trees, the simple thing to do is be prepared to loose arrows. Jason Westbrock is experienced with this--get in touch with him and he can help. He buys dowels in bulk and uses them for cheap squirrel arrows, with cheap feathers and cheap points.

Chad