Spent a lot of time trying to figure out where I want everything mounted behind the panel. One of my main goals was to keep everything I could in the first subpanel. Just easier to get to from underneath when everything is buttoned up.
First I created a mounting plate for the Airinc-429 adapter. Close to the center stack as that is where most connections come from.
Next up was the ethernet hub. the hub connects the two EFIS together and the XM Weather receiver also.
Then the WXWorx XM Weather receiver. Plenty of room behind the two EFIS.
Last but not least was the VP-200. This was the hardest to locate. I needed a spot where it was easy to get to the connectors. I finally settled on fabbing a mount which the VP-200 mounts to from underneath. This makes the connectors on each side easy to reach from underneath.