Also, I guess that is a pretty big gap between verbal and nonverbal. When I tried some practice questions (random fakey stuff off the net) with him in the week before the test), I noticed relative weakness on spatial questions. But the chess!! I don't get it. I mean, he is freaky good at that.

My instinct is that his strengths are generally more verbal especially *at this time for his age* (any 6yo who can read books 5+ years above grade will be verbally strong compared to other 6yos) but that he is able and competent with nonverbal skills, certainly in MG range. I wouldn't want to miss a problem, though.