Our experience was very similar with my DS, then 11. He had straight 19s on the VCI subtests so had an "extended norms" VCI, with a WMI almost 3 SDs lower and a PSI that was nearly 5 SDs lower (71 spread from highest to lowest scores). It meant a difference of 21 points between FSIQ and GAI.
We have taken him for a vision evaluation and are trying out vision therapy (he tested below average on a lot of the vision tests), but overall he is fine and we are not worrying about it. His processing speed issue doesn't seem to be negatively affecting his schoolwork or timed tests (he took the SAT, for example, and did just fine without any accommodations). So we are keeping keeping an open mind about hidden LDs but at the heart of it I suspect it's just one of those testing things.
