I bought the optional CO2 detector a few months ago but the instructions made no sense as they referenced different installations but now that I've been installing some of the avionics, it made a little more sense. Basically it involved crimping on some DSub pins and mounting the unit. I finished installing the G20A and then added the backup battery. I ended up removing the battery harness from that big bushing and looping it around the frame I just installed. I like that better.
Still trying to figure out how to tighten those screws in the transponder bracket without being able to get a screwdriver in there.
I also remounted the ROTAX fuse box.