I'm going to ask something, are you on Peaceful?
I saw direwolf with the same design for the slime farm, there was no problem sky
yeah... can mobs even spawn on conveyors?
That actually isn't true, Direwolf has done it many of times, he even has a personal spawner down in his base. In order to get them to be "Wither" Skeletons, you need to turn the exact copy on.Although you clearly have additional problems, note that MFR auto spawners will not spawn wither skeletons in the overworld. It will spawn skeletons.
That probably is the reason along with it being sunken down. Do you think it will work if it is hovering ABOVE some Extra Util. conveyors or water like my Soul Shard Spawner? Because that would be really helpful.[DOUBLEPOST=1376795547][/DOUBLEPOST]Thank you all for the help by the wayNope!
Conveyors are not a valid spawn zone, much like half slabs.
Do you think it will work if it is hovering ABOVE some Extra Util. conveyors or water like my Soul Shard Spawner? Because that would be really helpful.