How do I deal with Particle Board Subfloors and Hardwood Flooring?
If possible, try framing out the edges. I would remove all of the existing sub floor (since it is particle board) and then add addition framing along the edges as needed for the new plywood.  In cases where you can't meet a joist, go perpindicular and create a nice foundation for the floor to attach too.

I would make sure the floor has a firm foundation.  It might be extra work to do it, but I would take those extra steps if possible.