I intend to replace the wood in a horsebox ramp. The wood will be secured to a metal frame and then covered with non-slip rubber. I'm intending to use 18mm thick plywood. The wood will need to be strong because horses will walk over it to get on/off the horsebox. I was intending to use marine ply but am concerned that it may not be strong enough. Is marine ply usually stronger or weaker than hardwood ply ?