Thanks Simon again for the interesting and helpful information (your efforts are highly appreciated); I will definitively follow your advice and in case of problems swapping the driver OpAmps is not a problem at all ;-)
INU requires 115vac 400hz and +28VDC for initial turn on. Due to the high heating requirements at turn on, a lot of current will be required initially.
Do you have got an idea how much power is required on the rails? I have no problem with 115VAC/400Hz as
I built a powerful inverter, but currently its 28VDC output is limited to 2A.