Is the location of an aircraft spoiler really that vital?
Surfaces sticking out ahead of the Centre of Gravity act in an unstabilising manner: any dissymmetry will want to amplify itself. A dart thrown with the feathers first is in an unstable equilibrium and will very quickly turn around 180º. 

Surfaces behind the CoG act as stabilisers, keeping the nose pointing forward. An aeroplane has vertical and horizontal tail surfaces at the back just for this purpose. When spoilers are deployed at low speeds, the aeroplane is in a situation where you don't want any destabilising moments.

Aerodynamic behaviour is stable if a disturbance auto-corrects: a deviation is automatically blown back. Since motion in flight is relative to the Centre of Gravity, it follows that the aerodynamic Centre of Pressure must be behind the CoG.