Setting the kicking strap/ Vang for upwind sailing when the breeze is light.

Is the wind light? How to set the kicker (Vang for Americans) for upwind sailing and why for single handed dinghies with unstayed masts. Typically the Laser or ILCA, and Topper. Probably works for other boats as well. Light wind is from complete drift upto when you are constantly sitting on the side, and just starting to hike/ get your weight slightly outboard.