Control free and fixed static margin
The stick-free static margin depends a lot on the elevator hinge moment coefficients of the aircraft. Depending on the sign of the hinge moment derivative with angle of attack ($c_{r_\alpha}$), the stick-free stability can be greater than the stick-fixed stability (greater for positive $c_{r_\alpha}$ because then the control surface will deflect into the changed airstream). By how much depends also on the derivative over deflection angle $c_{r_\eta}$, but this one should definitely stay in the negative range, or the stick will be hard to center.

The stick-fixed margin is much easier to calculate. If aspect ratio is reasonably high, the surface-weighted mean of the quarter points of all horizontal surfaces will give a good approximation of the neutral point $x_N$, and the center of gravity depends on the loading of the aircraft. Normally, you would calculate the margin for both the most forward and the most backward cg location $x_S$ for which the aircraft is certified.

With the given planform, the mean aerodynamic chord $l_\mu$ is also easy to calculate, and the stick-fixed margin is (x backwards positive): $$\frac{c_{M\alpha}}{c_{L\alpha}} = \frac{(x_S - x_N)}{l_\mu}$$