The FAA has issued an airworthiness directive for the Gulfstream GII, GIIB and GIII requiring a measurement to determine the clearance gap of the exposed rounded portion of the doubler and clothespin fitting at the wing-to-fuselage attachment and repair if necessary. It was prompted by a report of an improper structural modification that had excessive gaps in the wing-to-fuselage attachment fittings, which could result in reduced structural integrity at the wing-to-fuselage attachment and consequent separation of the wing from the airplane.