Aerial Line of Sight Blocker?

[monchoman45]

So, I'm working on a new map, and I've come to a point where I could use an aerial line of sight blocker. I played around with occlusion heights for a bit before I searched for some clarification on Wikipedia. Wasn't much help. Here's what I came up with from playing with occlusion heights:

-An occlusion height of 0 denotes an object that all units can see through.
-An occlusion height of 1 to 32,511 denotes an object that land units cannot see through.
-An occlusion height greater than 32,512 denotes an object that all units can see through.

I assume that occlusion heights greater than 32,512 are see through because they're "taller" than the unit looking at them, and the unit is essentially looking "under" the object. However, regardless of occlusion height, I have been unable to create objects that block line of sight from air units. And due to the broad range of occlusion height, I'm not sure why 230 was picked as the number for a line of sight blocker, or why 400 is used for gates. Furthermore, all trees have occlusion heights of 230, except for Cityscape trees, which have occlusion heights of 300. I also noticed that all units have occluder heights, but these are all default 0 and seem to have no effect on line of sight blockers. Does anyone know how to make a line of sight blocker for air units?

Thanks for the help!