Get the Carinoids early or it'll be nearly impossible to flip them. I had 4 party palaces in their system and they just wouldn't flip. And since it was near the end of the game and I had given them quite a few ships, I decided not to invade.
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I am playing a game now with the Carinoids in the adjacent sector to my home planet. They flipped around 2186, with no culture modules built within 3 sectors of their home system. I did have 2 systems in their sector, and 3 systems in my home sector, but the two starbases in those sectors just had mining/production/defense modules built in them.
Regarding ships/starbases belonging to minors, when I go to the Diplo/Trade screen, I NEVER see ship/starbases for the minors listed, and this is with "neutral" relations with them. Are players not allowed to buy/trade for minor's ships/SBs?