Interesting thread. I recently bought a used Corona that had a Hitec GY-130 gyro. The first time I tried to fly it, it would just spin around. If I set the gyro to reverse mode, it would be stable but the control direction was backwards. That is, right stick would make the nose go left. I solved the problem by reversing the control on the transmitter.

Whats interesting about this is that I just installed a new G410T gyro and had the same problem all over again. All was well after I un-reversed the transmitter. What's noticably different about the G410T (as compared to the GY-130) is that its reverse switch seems to control both the gyro correction and the control input.

Did you try the transmitter reverse switch?