John,
   I have no specific expertise on the aero-dynamics or the hydraulics. but I did think about it when I had to choose between precise flight speed brakes and bill maddox speed brakes.  My conclusion was that you basically have two choices: a) guarantee that you have sufficient control authority to overcome unequal deployment b) mechanically guarantee that unequal deployment cannot occur.
    Precise flight has a sensor which de-energizes the system if there is split deployment.  If you are lucky, everything retracts.  This is not quite (b).
   However, on your system, since aerodynamic forces favor retraction, something like that might be a good direction.

Colyn