Switching to 8Mhz internal oscillator [solution]

[TomWS]

I'm just worried.
I wonder how accurate is the timing from internal RC, for fast communication like SPI (but the moteino is driving the clock, so there's no problem with synchronisation), and for synchronisation between moteino, if I plan to reserve a window for each moteino to communicate with the gateway, how often will I have to resync the moteino with gateway to avoid collision.

SPI doesn't need to be accurate timing, it is totally synchronous so the clock edges can vary widely even between pulses.

IMO, the collision avoidance mechanism in the radio, combined with sendWithRetry(), is good enough to avoid deal with collisions, but, of course, it depends on how you design your communication protocol.  Make it very stiff and brittle, something will break it.  Make it flexible and adaptable, you'll have more success with systems that tend to be somewhat stochastic.

Tom
UPDATE: Changed 'avoid' to 'deal with'.