Fair enough.
It's been quite some time since I've even thought about the 3.189 versions and such, so I'm quite rusty on thinking in those terms. But my main advice would be:
1) Try not to alert those planets before you go after them, and they will be smaller.
2) If you can survive it, try killing their command station early. Then you have to fight all their guys in your planets, but near your turrets instead of the enemy ones. Then you can mop up the enemy turrets after that.