Typically I tend to have one massive shipyard planet per sector. The mandatory two gencores to protect the planet is standard. But I scrap everything else and just have shipyards on the planet.

I do about the same thing as Sky, set one planet as the "Shipyard Planet" and uses the other planets in the sector for resources, troops, etc.

Ever destroyed every planet in the core with the Death Star? I got close but decided not to destroy ALL my own planets lol. Now thats general bombardment.

Did you beat the rebellion?