I managed to do some tricks to the USA curve by shifting the lat/longitude to a city that is on the east coast. I still can't change the peru/uruguay and Falkland Islands curve to curve upwards rather than downwards.
Guess it's a limitation with data densification.
You may have seen these other links, but maybe not using the same method:
Interesting reads. Thanks for pointing those out! the Macro seems noteworthy!