Peter,
Just to check the basics, once you've changed the Output Gain setting (or any setting for that matter), have you tried clicking the download button?
Whenever you change a setting on the Config&Flash screen, you have to download it to the KFlop, otherwise it doesn't alter what the KFlop is running.
It's also good practice to click the Upload button first, to ensure the screens show what values the KFlop is already using.