Second thoughts, not sure whether you mean daisy chaining two of 8-zone controllers together to get a 16 zone controller, or whether you’re referring to my issue of being stuck with having to use tap faucet controllers (unless I undergo expensive and messy directional boring under concreted surfaces for irrigation).
I suggest for information on the XR controller, you talk to your local specialist irrigation supplier stocking Orbit. I just did to ask about faucet controllers, and whether they will be able to operate as separate devices, such that they won’t turn on at the same time. The store spoke to their rep, the rep spoke to the guru in the US, and rumour came back that there’s a beta XR firmware which will allow faucet devices to not turn on at the same time, but automatically stagger themselves. On this basis, I’ve decided to finish my garden with 4 more faucet controllers, totalling 9, rather than installing a similarly expensive solenoid box and long lengths of blueline piping around my property.