When you are in the largest cog, if you notice the upper jockey pulley dragging on the cog, turn clockwise. This will increase tension and eleviate it rubbing the cog. What it does it changes the effective position of the derailleur and pushes (pulls? rotates?) it back further to avoid.

Think of two tangential circles stacked and meeting. You are moving the center of the lower circle down and back, causing the tangential points to seperate.

Does that make sense. After I read it again, it doesn't to me either, but at lease I know what it does. Can't explain it, but I know!

L8R