The 0.6 ohm coil is the notch coil, which floods constantly. I have the 0.5 ohm coil which is a "normal" wire coil and it doesn't have the flooding problem. While the idea of the notch coil is great, it is great for using in a dripper where the cotton goes through the center of the coil. Not so great in a tank where the cotton wraps around the outside of the coil. With the size of the notch coil, it doesn't leave much room for cotton so the cotton wrap around the coil is very thin, so the coil will continually flood.
I used to use the Cubis and Cubis Pro tanks all the time and did not get a single 0.6 ohm coil that did not flood. However, the 0.5 ohm coils works great.