Ok, update time:

Because I want to start on printing some some organically shaped models soon I'd thought the perfect test case would be a ball.
I modeled a ball (globe) of 20[mm] in diameter, but was unable to print it correctly:
I tried different amount of walls, speed, temperature, external fans, but nothing worked...

What kept happening was that the entire edge crawled inwards/upward the whole time.. so 1/3 in it would start printing outside of the ball because it had already crawled inwards too much.

Has anybody ever printed a successful ball and if so, can you tell me with what settings? This is really frustrating me - even though my final model doesn't have such a complex overhang, I would still like to be able to print this ball!