PE Gloomless 6 Cob 

S4: PP | PP | I - PP (9 | 9 | 18)
Setup by Hitori Dakeno.
To prevent imps from eating wintermelons, shoot cobs between column 7 and 8 so that cobs won't hit gargs too early. However, this makes the spawning of the next wave uncertain, which is main risk factor of the setup.
Wave 10: freeze the wave early, use a pair of cobs to protect spikerocks from bungees.
Wave 20: freeze the wave early (and kill ambush zombies), also launch 2 cobs to kill bungees.