You are right, Im thinking about South as Oceania, but I dont want it with one attack route only. This time it will be a more vulnerable fortress. So I think one route to Mato and one to Central Axis is fine... I could really block the attack route between Curitiba and Oeste Paulista or São Paulo...
About the blocked border between Mato Grosso and Central Axis, I will mantain it. Without it, Mato Grosso, a continent with only 5 countries, would be impossible to hold, because it could be attacked from many places. Central Axis already have 6 border countries, and can be attacked from 4 other continents, so its already very difficult.
5 is just a fine bonus for Northwest: 9 countries, 3 border countries, can be attacked from 3 places... Its my North America
Think about the continents this way:
Central Axis - Asia
Central North - Europe
Northwest - North America
Northeast - Africa
Mato Grosso - South America (more difficult, I know)
South - Oceania