With clustered structures, I would place them in front of the direction of a hostile phase lane.  Maxxing out your weapons, armor and fighterbays can leave you with a starbase that can be totally useless if the enemy can take your planet, destory your stuctures and builds theirs away from it. 

When fighting the Vasaris, I prefere to use srtucure upgrades along witth the contruction and docking ports to build and support Orgrovs when fighting a Vasari Kotsura.

Againts the Advent, auxiliary government can make them fight your starbase when their superior culture can destroy the planet but disallows them to capture it.

Because of the my distant star mod I changed my frigate factories to 0 so I build around 5 and since they create ships I usually put my starbase so that if enemy ships were to attack my factories, they would be protected by the starbase

Especially if you put your starbase a little bit behind a few turrets. If it's in front, it hurts you a bit because your starbase would be primaried by the majority of ships and your rear turrets would have trouble reaching. If you put turrets on the sides and slightly in front, some will take a bunch of fire from AI ships and will be able to reach farther. It's amusing when the AI parks Ogrovs within reach of Gauss

Hadn't thought of that.....  That would be a good counter if an opponent was attacking you with the TEC extended range missle upgrade with Ogrovs.  Nice.