NavMeshObstacle shape parameter like in Unity 4.x ?

Hello!

What is the best way to prevent the characters beyond the light barrier? this barrier is created dynamically at certain times of the game.


In Unity 5 there is a parameter called Shape that would solve my problem, but I'm using the Unity 4.
http://docs.unity3d.com/ScriptReference/NavMeshObstacle.html

Is there any elegant way to solve this problem or I will have to create a lot of NavMeshObstacles along the grid to block the characters?

Thanks