Pretty sure I've got an impossible one here, also not sure if it's been found yet, low on time at the moment, so I can't search this thread.
were from of
Has 1.66 upwards to the left gravity with a surface emitter and drone gateway with phantoms in two minutes, creeper hits the surface in just 20 seconds.
There are quite a few crystals nearby, I've not given it a go, and am not very skilled, but they may make it possible.
All of that is on medium/medium, for a less time, go large/high as creeper hits the surface in 4 seconds!