dave3825 is correct, there is no way to specifically say TG 2345 play on Left and TG 6789 play on right. The v0.6.1 final has a glitch in it that the stereo audio may/may not work properly. I emailed Denny (the author of sdrTrunk) about it and he said it was fixed in the nightly version. I downloaded the latest nightly about 2 weeks back and there is an improvement of the stereo output.
Jeff