In regards to the strength of OSB. OSB has been shown to be of an equal strength to plywood as a structural panel. This has been stated by the American Plywood Association. So, what is the reason that these engineers are not allowing it?
What they said to me is, with the new seismic codes coming in, it's no longer code compliant for the roof. The walls are still fine. Also, they could be installation issues as well. Most people don't know there is an aarow showing the direction of strength on the sheet for install.

