well i just beat the culling. just barely. it didnt help that towards the end i was low on gas, and i would have normally used the gas at the enemy bases i had taken out. unfortunately they were unusable because they were too close the the map boundary. fortunately i had strong defenses and i could just wait for enough trickle gas to accumulate to build a fleet for the final assault. ive started taking workers along with my attack fleet to build structures on ground taken. to prevent the enemy from sneaking a couple workers through and rebuilding everything. for zerg that also means building a hatchery, which kinda sucks. of course in this mission since i was fighting zerg i was able to build sunken and spore colonies in their creep before it receded.