Minecraft: Nether Mob Trap Concept - Ghasts, Pigmen and Magma Cubes.

While mining and gathering materials I tend to visualize ideas for mob traps etc and this time I decided I needed to try some builds and test out the physics involved.

After many partially successful designs I built a framework for a concept I think has legs and before I flesh it out more I figured I'd toss a video up and get some feedback from you guys.

Does it look feasible? Saw a major flaw already? Let me know.