You need to use a splitter cable so both Cosmoses receive the same signal at the same time.
Download to the first unit the main FW version COSMOS_M1.4.smf and download to the second unit the version COSMOS_Q1.4.smf
The difference with the main version is that here we have other settings for buffer lengths that with the same settings on both units produce in combination with the main version quadro-sound.
Feed both COSMOSes with one input signal using a splitter.
Outputs of the first COSMOS connect to the front stereo system.
Outputs of the second COSMOS connect to the rear stereo system.
Start your experiments with similar settings on both devices.
Then you can try different combinations of different settings.