I haven't tested this, so I'm basing this on conjecture. But anyway...
I would probably take out 3 grav towers and an elite charger and add in 3 stone towers and a pulvy. That way you can play your quicksands faster if you draw a tower (it's one of the problems I have with dark/earth denial: you can't play a quicksand for two turns), and any permanents the opponent DOES play will be destroyed. In fact, I might replace both an elite charger and a quicksand for 2 pulvys so you can draw it easier.
You would still have 9 gravity towers, and none of the gravity cards cost that much and there wouldn't really be any long-term ability costs other than pulvy (but that's only 1 gravity per turn, and since you're denying quantum, likely not even every turn).