What are the methods of attaching cable to OSB
Tear-out of the bolts isn't the primary concern here, even with standard flat washers. Sag is one, and complete snap-off of the sheet corners is another. 

If you must use the sheet without a frame, I'd move the cables inboard substantially--cantilever the shelf about 20% of it's length and width. This gives assurance that the corners won't break off and distributes the load much better. 

If you can't do that due to the load objects' size or shape, put a proper frame under the shelf. This can be as minimal as lumber under the front and back edges to spread load.