Unfortunately the picture is more confusing than clarifying 
Is this what you intended to post? There’s no navigation information on the image.
But I think I know what you mean. Currently the only way to relax Z-axis checks in pathfollowing is with C++. You need to derive a class from UPathFollowingComponent and set MinAgentHalfHeightPct to something more than 1. I’d start with 2 in your case.
Cheers,
–mieszko