This may not be official but here is a little background of the OB markers.
We have always played and planned for OB to be the path. When we went to place the OB markers, we were told that they could not be on the path line because this was to close to allow vehicles to pass on the path. So we moved the OB markers in but planned to still play the path as OB as well.
As for the meadow, the same situation comes up. Because of mowing we can not put them on the exact mow line. Therefore the meadow rocks are like the path rocks in that they are located off of the actually line of OB.
As for the trees to the left of 15, the stone are located between the big trees that are the actual line for OB. They are technically on the line.
So in Summary:
The path is OB not the rocks on 2,3,4,5,13,14,15,17 & 18.
The meadow cut line is OB on 11,15 & 16.
The rocks mark the OB line of the trees on 14,15 & 16.
When we play the Safari there will be rope hung to mark this so there is no confusion there.