F(a) = Force of wind on kite
p = density of air
v = Airflow velocity at kite
A = Surface area of kite
CL = Coefficient of lift of kite
Note that the airflow velocity is squared for the calculation of the wind force on kites. Hence, if the airflow velocity is doubled, the wind force on the kite quadruples.
In a constant wind, with a given surface area, the route to increased or decreased pull is through the coefficient of lift. In practice, this is achieved by placement of the fin's towing point.