Columbia,
Is this more or less what you're looking for?
I edited the mesh slightly to get all four sides of the post the same, and then assigned the post to channel 4. You can now either have the fence posts match the walls and keep the border, or you can make them solid to match the outline/cap/rail colour instead.
Here's the package file if you think it will work for you. It only contains the files necessary to implement the changes. These files will override the original files, so if you've already used the fence, you will probably need to delete and place new copies and/or possibly clear the game caches in order for the changes to work.
I also updated the matching Farmington gate on the sides that face the fence.
NOTE: Only works in games that have the "Outdoor Living" stuff pack installed.