Starting at the recognized issue of homework taking very long, trends I've seen here that fit that along with the lower PSI and WMI scores are perfectionism or stealth dyslexia or possibly a variant of dygraphia or a very strong need for meaningfulness/relevance to be fully mentaly engaged.
At core, scores are subtests that have your kid doing something specific and rating them on that. Without other evidence I wouldn't view PSI (which includes a test of writing numbers in sequences) as an indicator of a gifted kid's actual processing speed anymore than WMI (time delayed memory of meaningless data) is a direct measure of his full blown working memory.
