Quote Originally Posted by 1pain1Duck
They're good in helping you hold your castles against big odds.
Also I prefer to use a system where I have a central army stack that is surrounded by provinces with upgraded castles and small garrisons. This usually creates a situation where I can use less men to protect a much larger border.

Like when playing Poland I tend to have one elite stack in Poland and then have upgraded castles in Volhynia, Prussia, Moldavia, Silesia, Pomerania. I find it to be a rather cost effective way of defending a lot of land.
Awesome idea... you've just helped me put another edge into my game. I usually keep these large defensive armies but they'd hemmorage money that I could have spent in other ways. I'll try your hub system for defense.