If ony it was as simple as that when there is on-board mixing, two motors and an aftermarket product with no diagnostics or push-button reset.
Unfortunately it isn't and taffybouy can tell you.
Here is how I would approach it:-If one motor turns the wrong way AND only one relay energises in reverse throttle then, disregard which motor actually rotated in the correct direction. Swap wires on the motor that engages its relay coil when throttling forward.
If you now have both motors rotating the wrong way then toggle the throttle reverse switch on the transmitter so you can have both relays off at forward.
You can then procede from there and crank up to 100% gain & use the relay clicking as a guide to:-
- zero the rudder trim and
- trim the throttle midway between the relays clicking before reverse and forward throttle
- repeat if needed
The sbec before switch ensures the R3FS is settled before the main board is powered up. The procat controller should allow for that but a reset delay can be added if it misbehaves. The same behaviour would show up if the switch is left ON and power comes on by battery connection.