Sorry to bump up this necro, but I want to clear up something that is incorrect. Spawning slimes/magma cubes with the MFR Auto-Spawner and killing them with the grinder, they do NOT split into more slimes/cubes. Once the grinder kills the slime/magma cube no matter what size it is, it is gone. No little ones. I had this idea after hashing out my design and found out it did not work. So I put vanilla spawners at the top of my structure (with drops and conveyor belts guiding them down safely) and 50 (yes 50) nether portals using the same conveyor system to take advantage of the random pig men spawns from them. Of course, I need to be near my structure for this though but it's free essence to use for the spawner which I mostly use for endermen, ghasts, wither skeletons and magma cubes.