Hi Dubgirl,
If you have the 360 main box and a mini box you need the main box to be set to fast start or active start so the mini can access the recordings on the main box.
If you have upgraded 2 V6 boxes to 360 you can specify which boxes the recordings are recorded on and I assume you would need them set to fast start or active start to watch recordings across boxes, I have a 360 and a mini box so can't speak from experience on that setup.