Sure, you want to go to Data\Xml\Buildings, and edit the 4 starbase files "Starbase_Empire", "Starbase_Rebel", "Starbase_Underworld" and "Starbase_Pirates". For the Golan 2 entries and the "Minor_Starbase_Template_LVL4" entries switch the tech level from 2 to 99. This will make them unbuildable.

Note this won't change the starting Golan 2 and 3 platforms - for that you would need to replace their entries in Data\Xml\Campaigns folder.

Thanks- It's the only part of the submod I'm not really fond of :)
I was to surprised to see a Rebel Pelta frigate. Nice work :)