Thanks, Mich, for your thoughts. These are very helpful. A few responses to your questions...

Originally Posted by mich
Does your son have any grapho-motor troubles? Have you had his vision checked?...
To be honest (feeling really stupid at the moment!) I don't know what graph-motor troubles would look like. I will look into it though! We have had his vision checked twice (just a regular eye exam) and they didn't find anything wrong.

Originally Posted by mich
Lot's of horsepower, locked in a bottle neck...
Great image!!!

Originally Posted by mich
How are his literacy skills? spelling? math facts?
His literacy skills are great (reading level and comprehension around 7th grade), math skills are at about the 3rd or 4th grade level, and spelling around the 4th grade level. So all of those areas are quite strong. Does that show something or rule something out?

Thanks again for your thoughts and help!