Very creative, and useful post!  Another tip:  Look where you're GOING, not at obstacles. If you look at obstacles, you will hit them!   My off-road course is in the middle of an old pear orchard now going back to natural. Oak trees and shrubs all around. We laid out the course around these obstacles, and having learned our lesson from our previous bash spot, we took some old cheap foam camping mats, cut them into 10in strips, and wrapped them around the base of the trees. We also put orange cones INSIDE these which causes the impact forces to be directed UP. Best thing we ever did for eliminating hard hits while running hard.