[CUJO_1970]

Do you know for a fact that they did parachute cargo from the cargo door or only from the regular door that the parachutists used?

No, sorry I don't.

I've searched quite a bit and have never seen the cargo door open in flight however. The door is split horizontally with the top door swinging upward and lower door swinging downward. This would seem to preclude it's use while in flight but who knows?

Will continue looking to see if I can find anything...