Hello,
I, like many others have been struggling getting my kik an snr to be MONO using SD3 in Logic and I found a way to make the “stereo” outputs “mono”. I noticed there are a few other topics about it which kind of degenerated into a flame war so hopefully this will be more useful.
Right click on the pan pot of the stereo aux output and select “stereo pan”. You’ll notice the pan pot change. Centre the pan pot. See screenshots for what i mean.