Well actually, 6 x 7 is the question. At least in one of the later HGTG books when they rebuild earth it's alluded to that this was the question all along.

Although someone from the Green Party started the transition (Jan Philipp Albrecht). But nice to see them embracing it.

Are you sharing files between the same devices often? Then syncthing might be useful here. You can set it up to keep a local folder in sync between multiple devices using you local wifi. If you are sharing to new devices frequently, then it's too much to setup for your use case.