Question

I once heard that one Torah scholar told another Torah scholar that in his community the custom is to add extra myrtle branches to the Four Species, in multiples of three. Some go up to 6, and some to seventy-something. So the other one answered him that this is "do not add." I don't remember what he answered back. But "do not add" applies only if you add a fifth species, right?
What would the ruling be regarding 2 etrogs, 2 lulavs, 4 willows, or 3 willows, and 4 myrtles?