I am actually working on my G3X / ACK E-04 installation this afternoon. Section 18 of the ACK installation manual is pretty straightforward. Figure 20-2.2 in the G3X installation manual shows the ACK E-04 ELT connected to one specific RS-232 output as an example, but you may use any available RS-232 output on any GDU display, as long as you configure it for the "NMEA Out" format. This data is output at 4800 baud, so you may need to change the baud rate on the ELT as described in section 6 of the ACK installation manual.