What are reasonable values for the position of an airplane's center of gravity compared to that of its center of lift?
If I understand your question correctly, h is a fraction of mean aerodynamic chord c. That fraction can be >1. It could be that the aircraft is stable with a huge download on the tail.

The mean aerodynamic chord is an aid, to simplify calculations. It is not a hard limit for the equilibrium points. Whether the value is reasonable or not is hard to say without having seen the full problem to be solved.