It doesn't have to be the same image. Vix makes it a bit easy. Let's see. I'll hit the menus......
One the remote receiver. Menu>Tuners & Scanning. Fallback Configuration. Enable fallback remote receiver.
Set it up to your main receiver network config.
Probably best to set the main receiver to a static IP address. Or in your router, setup to assign an IP based on MAC address. Would suggest the same on your client (remote) receiver.
Go back to Tuner Setup. Down at the bottom, click Client mode.Enable it. Set it up to see the main receiver.
That should do it. I can parallel it here if you reach a bottle neck.
It doesn't have to be the same image. Ex. I ran OpenATV on the mio (main receiver) and Vix on the remote. But since Vix is so cool I migrated to the same image on both boxes.
If you use picons. On the remote receiver you may have to FTP or import your channel list from the main receiver. I dunno. It took me a bit to get it all working like a peach. And a peach it is!
But as I mentioned. The main receiver should be in standby mode.