So the problem is that the master and its slaves may have different times due to latency? This would mean that the master is performing the same task as its slaves. Why not just have a separate master that only acts as a clock and outputs to the other Arduinos at the exact same time? I mean you could just have a simple digitalout wire and then attach a lead from each slave to it thus each get the signal at the same time. I think. I'm really new to this stuff but that seems like an easier way of doing things if it would actually work lol.