My daughter has a large disparity between her FSIQ and her GAI too. She is also a perfectionist but shows no symptoms of ADHD or LD.
Here is an interesting link about using the GAI in place of the FSIQ.
http://www.nagc.org/index.aspx?id=2455The weight of processing skills in the Full Scale IQ calculation has doubled, with a consequent reduction in the weight assigned to reasoning tasks (verbal, visual-spatial and mathematical). Testers of the gifted know that abstract reasoning tasks best identify cognitive giftedness, while processing skills measures do not. Gifted children with or without disabilities may be painstaking, reflective and perfectionistic on paper-and-pencil tasks, lowering their Processing Speed Index scores; to a lesser degree, they may struggle when asked to recall non-meaningful material (Digit Span, Letter-Number Sequencing), lowering their Working Memory Index, even though they excel on meaningful auditory memory tasks that pique their interest. 
