See also APA docs.
See 2007 CBC 2304.7, table 2304.7(3) footnote f
f. Tongue-and-groove edges, panel edge clips (one midway between each support, except two equally spaced between supports 48 inches on center), lumber blocking or other. Only lumber blocking shall satisfy blocked diaphragm requirements.
i should have clarified , supports are 24" OC and min 1/2" ply is used. i did not realize the clips or min 24" wide piece was required, though!