I was running some numbers on the Drengin Slave Pit and its upgrades compared to power plants and it is sad. The slave pit gives the same adjacency bonuses as the power plants but doesn't receive any bonuses or have any bonus of its own. This makes it extremely weak. The fact that it also benefits research is nice, but because the Drengin still get the Cooperation Center line of improvements, it actually helps science much more than manufacturing. I like the idea of the Slave Pits, but it needs a straight-up buff. The slave pits should be worse then the power plants with only a couple of adjacent buildings, but should become more effective as the bonuses build up.
After looking at the numbers I believe the adjacency bonuses for the slave put line should be as follows:
Slave Pit: +6
Slave Mill: +9
Slave Factory: +12
Those numbers might look a little gaudy at first, but at every level, they need 3-4 adjacent manufacturing buildings to surpass the power plant/factory equivalent, even factoring in that Drengin manufacturing buildings are better than standard factories.
