I haven't read all of these posts, so this may be a repeat.
The Forbidden Palace is a cool thing. The problem is that the city that you want to build it in is likely outside of you Palace's sphere of influence and curruption has your production in that city to one shield a turn. Here's one way to fix this problem: The Forbidden Palace can only be built once, but your Palace can be rebuilt as many times as necessary. So, build the Forbidden Palace someplace close to your Palace where the curruption is not bad and then build your Palace on the edges of the new sphere of influence (where curruption is bad but not crippling). When you get the Palace built, the sphere of its (and the Forbiddent Palace's) influence now extends much further than before. You will probably even need to rebuild the Palace again a little further away from the Forbidden Palace for maximum affect. But now the same city that would have taken 200 turns to build the Forbidden Palace will take a LOT less time to build the Palace. This whole operation should take no more than about 75-100 turns especially if you can overlap the building periods of the Forbidden Palace and the Palace.
The Forbidden Palace is a cool thing. The problem is that the city that you want to build it in is likely outside of you Palace's sphere of influence and curruption has your production in that city to one shield a turn. Here's one way to fix this problem: The Forbidden Palace can only be built once, but your Palace can be rebuilt as many times as necessary. So, build the Forbidden Palace someplace close to your Palace where the curruption is not bad and then build your Palace on the edges of the new sphere of influence (where curruption is bad but not crippling). When you get the Palace built, the sphere of its (and the Forbiddent Palace's) influence now extends much further than before. You will probably even need to rebuild the Palace again a little further away from the Forbidden Palace for maximum affect. But now the same city that would have taken 200 turns to build the Forbidden Palace will take a LOT less time to build the Palace. This whole operation should take no more than about 75-100 turns especially if you can overlap the building periods of the Forbidden Palace and the Palace.