This is not my 2008 Seneca but I happened to run across this other guy's photo gallery of his 2008 Seneca over the weekend.
Here is a pretty clear picture of his add-on compressor setup; https://onedrive.live.com/?cid=0C1FD...%21217&o=OneUp
You can zoom in for labels and detail.
He has some other really great pictures of a larger inverter, solar panels, and other mods. There are actually 154 pictures total of various things he's done.