miguportugal, why don't you order a heatsink with longer fins? Not 5, but 15-18 mm?
you are wright but i dont see in ebay and buy the other.
the contac area (chip-heatsink) is not enough for oc.
a lot of air flow dont makebig diference, the heatsink is cold but the sensor is at 55º
my fan with only with 7V to full power the diference is only 5º at 412mhz