Overlapping "Ground"

In my map I have my hills and other walkable features of the map placed on a large plane. (top of hill and ground plane are both “ground” layer, i have tried top of hill as obstacle too…)

whats a good fix to this? or should I just cut out the ground plane from all the hills and any other assets… I could do this but it will make the floor a lot more polys.

img here: http://imgur.com/cMU1j

oh it looks like its actually having probs with the “safey cushions” on the side I use to keep units from falling off, should I have them hovering above to not collide through anything?

is this the best way to keep 'em from falling down a level

pic: http://imgur.com/83RV3


I’m not sure I understood the original problem really. But in 2. Yes that looks like a working way to keep units from moving away from the main path between those colliders.
Also, the red artifacts seen in the first image: from what I have heard, that was fixed in Unity 3.5.3J, what Unity version are you using?

3.5.0f5 eep need to upgrade