Wing area is a "square" factor of scale.

Appropriate wing loading is based on a "cubic" factor of scale.

If the scale is doubled... the area you get is (scale)^2 or 4X the original. The load carryable by the model is a factor of (scale)^3*K.

"K" is a coeficient of the airfoil and the wing design. (I made up the variable... I'm sure there is a huge long formula to replace it somewhere) K will be some value less than 1.0

You can experimentally determine K for any given wing planform and airfoil combination.

This assumes the same airspeed and angle of attack at all scales....