Dammit.
I hope those not familiar with the 20k principle got a few hints from the game. Especially
1) If you go for the first city to be the 20k city, never build more than one settler. Build maybe one or two warriors and nothing but culture after that as long as there is culture to build.
2) Don't focus too m uch on wonders, rush the normal culture buildings as soon as possible in order to let them double early.
3) Try to keep the tech pace low at all costs. This does mean never trading monopoly techs away, keeping trade actions low in general and fighting phony wars (which hasn't been done, but Spain had the other continent under control to early).