We used to do 4/1 to extend fly, because the normal fly cycle is 2 kicks per arm stroke (unless you're Tom Malchow who only did 1). The problem with this is you get out of the flow of the stroke, and end up having to muscle it a lot because there's no connection, and you really have to watch your technique so you don't just turn it into dolphin dives.

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I wrote this, you should read it:
https://www.slowtwitch.com/...n_Swimming_6700.html