My fighting floor surrounds a 3x3 pitfall with 50% pillars, 4 high. I'm going to remove the top pillar segment in the middle 3 pillars of two sides, and install a blade trap upside down on the ceiling, on both sides. This ought to whack the zeds as they fall down past the blades and hit the log spikes (which are inverted to give me a flat floor). Anything that stands on top of dead zeds or gore blocks before I can remove them, gets its head lopped off too. The only danger is that a blade trap will fail and leave a 3w x1H slot missing from the top row of pillars, allowing spiders to escape, if I don't reseal it pronto. I've never done it before, so its worth a try.