it's working very well when i got 2 very distant points but when i got 2 very close points i got some visbility issue.
here is a picture showing you what i mean : http://img42.com/zcX0d
you can see a huge arrow from france to the US and a very very small one from France to France.
is there another [magic] function like the last one that allow me to have a bigger curve (when i want to) to increase it's visibility ?
i think i can do it by changing the ellipsoid or the height, but i failed painfully when i tried some options blindly (i don't really understand the math behind 
).
if you (or someone else) have a clue it would be awesome