I have been using fluoro for several years for stillwater and stream fishing and rarely have a knot come undone. I have used the improved cinch and loop knots with nary a cork screw. But, I keep reading about the failure of fluoro unless certain knots are used. So, in studying the Frog Hair site, they list several knots for flouro, based upon their research. Additional knots. OK, a few more. Remember to wet the knot as you pull it tight.

Eugene Bend Knot