UR-RT4: Setting output levels via DSPMIXFX

Hello. On my UR824, I am able to set the output levels for each of the four pair of outputs in DSPMIXFX. Raise or lower the db as needed.

On my UR-RT4, I realize the Main Output and Line Output 1/2 are Mix 1. Only Output 3/4 is independent, using Mix 2 . But there is no place to adjust their line outputs. The only level I can control in the setup is the Line Input 5/6.

I ask because my Output 3/4 seems far louder than the other outputs. When I am in CUBASE Control Room, assign 3/4 to a cue but then assign the main mix to the cue, it is way louder and I have to bring the level for the cue down very low.

It would be much better if I could set the level via DSPFXMix. Am I missing something?