I was watching some photos and I found this one
http://www.carrierbuilders.net/gallery/20050811_F-18E/post-7-1118515677.jpg

Look at the underwing tanks: is this their actual position or is it a mistake of the modeller?
If it's true, does this have an effect on the aerodynamics of the real vechicle?
I thought this could be necessary because the aerodynamic flow around the fuselage could determine the tanks to collide when jettisoned... what do you think?

According to the McDonnell Douglas brochures I have, those are the attachment points.



You assume correctly that this will effect the aerodynamics, but anything and everything attached to the exterior of an aircraft does effect the aerodynamics.



The configuration shown is a "ferry configuration" and would "hopefully" not involve tank jettison, but there are prescribed maneuvers for jettison.

You're on the right track. When the engineers at McDonnel Douglas designed the Superhornet they put the pylons too close together. While conducting weapons certifications they were having problems with the weapons colliding after release. They couldn't move the pylons apart any more because pylons 2 and 10 are right up against the wing folding hinge. So they angled the pylons out 4.0 degrees to create some space. They also canted pylons 2 and 10 at 3.5 degrees while the rest of the pylons hang straight down. This created more space but is less aerodynamically efficient.

Basically the engineers screwed up.