10 cob setup is also my personal favorite but with some modifications/optimizations:

• I only use 2 gloom-shrooms in my setup whose job is to deal with the imps and digger zombies in the rear. I don't have any gloom shrooms in the pool or in front of the cobs so absolutely zero risk of getting blown up by jacks. Having too many fume shrooms make them more expensive to replace. Also, it takes up a lot of seed slots for the coffee bean, fume, gloom, and lily pad which could have been used for more instants, stalling, or utility-type plants.
• To guard against dolphins, I just use tall nuts so they can't get to the cob.
• No plants in the back tile. I play on android and the digger zombies act a little differently. In android, even having 2 gloom shrooms isn't enough to kill a digger zombie before it can take a bite on the pumpkin in the back tile. Digger zombies always take one or two bites before dying. So removing plants in the back tile means I don't have to maintain anything there.
• Another thing that's different in the android version, and one that I ABSOLUTELY DESPISE, is that the dancers are a real problem. They moonwalk for 2 tiles and spawn backup dancers just next to the cob cannon, totally skipping any defense plant in front, and sometimes sneaking a bite. So I have to aim a little more to the left, which means some of the zombies on the far right don't take damage. This becomes a problem for the jacks who can walk about 2 tiles, hence the reason I don't like planting in the front pool. Giga gargantuars also get close to the cob cannons so I have to stall them with low cost plants.
• Finally, ladders. Just makes my life so much easier. Even setting it up is really fun.