Ok, here are my new findings:
1. The 3072x768@60Hz *is* one of the default modes stored in the TH2G by default!
However, the mode won't be effective unless you specify the modeline in the xorg.conf.
The appropriate modeline for 3072x768@60 is:
ModeLine "3072x768" 195.00 3072 3144 3384 4032 768 771 780 806 +HSync +VSync
2. I have created an xorg.conf (attached) with the 3072x1536 resolution that works
fine with my six Acer panels where one of the LCDs has been connected trough
DVI->VGA connector. The scaling works fine in that mode. I guess you can
safely assume that the other five outputs will also work with the adaptor :-)