This is the Survival Endless setup I'm using right now. (Basically. I decided to abandon the Spikerocks and replace the Spikeweed/Spikerock seed packets with Cherry Bomb and Doom-shroom seed packets.)
We all know those Winterbox/Ice Cube builds that store a bunch of Ice-shrooms in spots to activate when necessary. What I thought was, why not take it a step further? Instead of storing Ice-shrooms, why not Doom-shrooms? When properly positioned, they can take out the whole field of zombies, usually. Sure, they leave a bit of toxic water, but you can wait and plant on those afterwards. I'm thinking about stockpiling my Doom-shrooms in the 4 spaces in front of the Tall-nuts. I haven't tested my idea, but I'm planning to and I'll post an update when I do.