Why don't use unit instead of trigger?
Import the dummy.mdx model, then make a unit with the dummy model, set the scaling to 0.1, else to 0, attack enabled to none, move type to none,and then set up the shadow of the unit, also dont forget to make the collison size of the unit to 0, and it must have locust ability
It more easier than use trigger...
I know that the trigger would look better, but using the power of the object editor is also useful