i have created my own based off testing of mob spawn and despawn times, this is how i managed to manage it.


This is the platform spawner in its current condition, building more floors soon



This is the clock that holds the pistons out for 80 seconds, and in for 8 to allow water to wash the spawn floors.

every 80 seconds i get 7 mobs per floor on average, sometimes more. imagine how big this can be with almost no limit besides 128 blocks of spawning area? this is only taking advantage of a small piece of that area.