Flight model stability issue with ordnance

[mppd]

I have been toying with a T-28D flight model for someone elses future project, and found a fine combination of values to make it fly just fine in clean configuration.

 

However, throw some ordnance on it and it starts to wobble after rotation and just plain flies unstable in the air. Tried shifting the CG forward a bit, which helped (the weapon stations were a bit fwd of CG) but still not what I think it should be.

 

Anyone with a helping word on this for me? I sort of miss the MS Flight sim "stability" values. The roll damper value simply dulls the roll rate and doesn't really help this basic instability. Once the underside is clean, flies fine again.

 

Thanks,

Mike D.