Always follow your wing manufacturer's recommendations regarding weight ranges. Each size of canopy is certified for a specific weight range and flying outside of that range means you are flying an uncertified aircraft.
The basic rule is to choose the wing size so the takeoff weight is in the middle of the weight range. Less weight on the wing (lower range takeoff weight) can be considered for foot takeoff, when flying in calmer conditions, or when you want to improve economy. More experienced pilots who want to fly dynamically, have higher speed and fly in more demanding wind conditions can consider greater wing loading (takeoff weight in the upper range).
