I don't know for sure if there's any solid research, but the first place that comes to mind to look would be in the realm of the work of Linda Silverman re: visual-spatial (right-brained) learners. I vaguely recall that she usually cites to lots of sources, if you're looking for hard core research. Dyslexia, among other LDs, would seem more common among right-brained learners from the way she wrote her book Upside Down Brilliance (which is out of print but it's a fantastic book - I have it, and it is a bit of a life-changing book for me - sometimes there are used ones on amazon).

I have two left-handed kids, DS5 hasn't even really started writing yet (will be getting OT) and DD6 has pretty good handwriting, though I'm noticing her grip is suddenly rather poor. They are both VSLs. DD is in vision therapy for eye tracking issues, and it has helped a lot. I think her ocular motor skills are far better than mine at this point (LOL I can hardly do some of her exercises) and she's finally reading at grade level (though we're hoping to see further improvement, more in line with her supposed potential). My kids have had their fair share of motor issues/SPD and left-brain weaknesses (auditory processing, primarily).

I don't know if letter reversals are still common at 8.5.

The group of issues you mention, physical uncoordination (motor issues), dyslexia and handwriting, do seem to be associated with right-brained learners from the way Silverman discusses things (or perhaps I'm muddling VSL issues with SPD issues). Have you checked http://www.visualspatial.org/ ? Specifically, I'd look at http://www.visualspatial.org/Product_Marketing/RTTK/kidquiz.pdf and http://www.visualspatial.org/Articles/appendc.pdf . If your GS is a VSL, you may find several helpful articles on the website.

smile