[Suicide Junkie]

Ok: here's the lowdown on facility stacking for you:

1) Nature shrines are ONE PER SYSTEM EFFECTIVE.
2) Value improvement plants are FULLY STACKABLE.
3) Conditions improvement are FULLY STACKABLE.
4) Training facilities TAKE HIGHEST VALUE on a planet or vehicle. They then WORK INDEPENDANTLY between planets/moons.

#4 could use some clarification:
NOTE: Some of the following facilities do not exist in the unmodded game, and are here to highlight features of the system.
EG: A planet has two Training facilities:
one rated at +1%/30% max and one rated at +3%/10% max.
That planet's moon has one Training facility rated at +3%/20% max.

The planet's facilities are combined to produce an overall effect of +3%/30% max.

1) A ship sitting in the sector will recieve +6% training per turn for 3 turns. Total: 18% experience.
2) On turn 4, the ship will recieve only 5% experience:
2a) The moon's training facility gives +3%/max 20%, thus adding 2% to get a total of 20%
2b) The planet's facility then adds 3% training to get 23%.
3) Turns 5 and 6, the ship recieves 3% training: Total: 29% experience.
4) Turn #7, the ship gains only 1% experience, and reaches the final max of 30%.

Q: Is it possible for step 2 to work the other way, and have the planet give its increase first, which makes the moon's increase useless?
A: Possibly. I haven't done enough testing to work out the timing details.
I suspect that the facility with the lowest max is applied first.

Any Questions?