Hi Michael,
the point of the mod was to bypass the 3 buss section completely but still be able to hit a switch and revert back if need be. Saw it done once and the facility shutdown before i could get the techs number and schematics. Also on the 6k there is no pre or post input on the vca nor is there an input to access the compressor pre or post, thats the big difference with the 4 and 6 aside from the 3 buss.