Hello @ncav , and thanks for using the Forum!
After reviewing your explanation, it appears that the method you are currently using is the appropriate approach for calculating Lift and Drag coefficients when working with half geometries.
If a full model were to be used instead, it would be necessary to double the reference area. The total force (N) would also double by calculation, resulting in the same Lift and Drag coefficients being obtained.
I hope this information is helpful to you.
Best regards,
Kaan.