My OKAP scores were always less than 30th percentile. I passed the boards at 60th.
I used the Friedman book and Will's course notes, supplemented it with the Academy books. Did all the Chern questions at least twice and also used the Mass Q and A book. Last minute optics for optics combined w/ Will's Guyton optics. The last week I used the new Kanski atlas with case studies, it's a great review.
Will's retina, path, uveitis, and oncology sections were great, although cornea was very poor so use something else for that. The Eagle Pathology CD from Wills is money. Also the REDAtlas is good for retina and cornea. I would review peds and optics again right before the exam.
I started hitting the studying hard in November, so by the time the Wills course rolls around it's more of a review for you. Good Luck!!