RE: Power Expander or not -that's the question
I think it is very difficult to figure out exactly how much current flow we need, there are just way too many variables. This is why I simply supply 3 amps to each servo, and then go fly, knowing that this is more than enough. (Sorry for saying it yet again)
It just takes a little thought and planning to make sure that each component you are going to use is up to the task. Check the manufacturers current flow ratings for each individual component.
Jim