Reynald's number
The coefficient of lift is a dimensionless number that summarizes the effect of the airfoil on the lift of the wing. The lift force is equal to one half times the air density times the air velocity squared times the wing area times the coefficient of lift. the maximum lift coefficient is the lift coefficient just before stall. The maximum lift coefficient determines how slowly the plane can fly in level flight. The maximum lift coefficient determines how tightly an aircraft can turn at a given airspeed. Model airfoils can't usually achieve as high lift coefficients as full scale airfoils because there is less energy in the airflow and the flow seperates from the model airfoil at lower angles of attack which correspond to lower coefficients of lift.
A highly cambered airfoil like the S1223 can achieve a lift coefficient of 2.2. Its practical application is limited to load lifter type model aircraft.
There is not a lot of reliable wind tunnel test data of model airfoils at large flap deflections. Therefore it is hard to say with assurance much about the associated maximum lift coefficients. I think it is safe to say that flaps on models could produce lift coefficients above 2.0 and possibly as high as 2.5 or so in some cases.