You only really need accumulators in the rear. I ran 1/2 inch line to the accumulator and then 1/4 inch line from the accumulator to the cylinder and it made all the difference in the world.
If you don't run the 1/4 inch airline it doesn't work the same, the small air line slows down the air going in and out of the accumulator and kind of acts like a shock.
Of course it does slow down the lift some and uses more air but it is worth it to drive the car without having the back end bounce around over every bump.
I just used Firestone 1/4 gallon air tanks.
http://www.truckspring.com/1-4-gallon_297.html
It also helps in the front if the valves are in the back of the car instead of near the front.
The cylinders use very little air to lift the car so when it hits bumps they compress and spring back up really hard. The more air you have to squeeze the less erratic the bump.
I started with 1/2 gallon accumulators and it was so soft that it was creepy feeling when driving. I could put my knee on the bumper and push it to the ground so 1/4s are the way to go.