Heres a better way...
1) make some extended terrain so it looks like its a higher drop from the top of the cliff...
2) Place a barracks so it looks like its hanging of the edge...
3) Do The Lift Glitch So the shadow disapears
4) Create and Lift another barracks lower where you want the shadow to be...
5) Disable the lower one so you can only see the shadow
6) It looks like its floating HIGHER!!!