This mod does work but unfortunately it only works w/ the AC3-RF input only (coax & optical digital inputs are non-functional through the new output).

I would recommend pin 9 of IC5 to access the digital output as this is where the input switching works and thus will be able to use the processor as a full blown switcher to pass all your LD digital sources through it (DTS, PCM, and AC3). Also, you can access that pin from the top so there is no need to remove the board.