If you want to be flying in sub-five knots I would say you are looking for something a little 'larger' like a Super 6/8, maybe even a 10. (All dual line and miracles can be performed!)
That said, using a lighter line with your stunter is said (by some) to do the trick! What I used to find though is when the wind completely goes, the lines go slacker than with a heavy line and bang you're on the ground. I use a 200lb line with my Sholtz signature in all weathers.
You could of course be flying in the wrong place. It's amazing how wind can change, even on the same flying field. Try moving around out of the way of any obstacles (trees, buildings etc) and you will find something better.
happy hunting,
Mr. Chaser