I'm looking for method(s) to determine the CG of any fixed wing aircraft for it to be reasonably stable. I only know for conventional aircraft, placing the CG between 1/4th and 1/3rd of MAC behind MAC leading edge usually works but when it comes to unconventional configurations like canards or tandem wings or even more lifting surfaces I don't know what to do.
I drew some examples to ask what kind of approach should I use for each of these aircraft configs to find their desirable CG position.
Also how can I decide if a surface is better suitable as a positive or negative lift producing surface? For example for a canard we know that both wings produces +lift but if we shift the CG on the forward wing as if it was a conventional airplane the main wing becomes a down force generating surface (assuming it can fly) doing that is obviously wrong but when it comes to model B or E it gets blurry for me.