Check out the speed of the Fly leg kick on these videos. These videos show that Butterfly kick is the 5th stroke as it can be done faster than the world record.
Hill Taylor (Lane 7) - 50m Long Course Butterfly Kick on back in 23.10 (Liam Tancock's LC World Record 24.04)
Ryan Locte - 50m Short Course Butterfly Kick on back in 20.80 (Peter Marshall's SC World Record 22.61)
This is what you should be aiming to do for the first 5 metres of every push off. This is what gets pb's and medals. You should all try and aim to beat your rival in the next lane on each push off during training by racing the first 5m kick feet to flags.
Kevin, Tom, Elysha