Don't triple post please... I collapsed your posts into a single one but don't let this happen again. It was purposely, because the messages were different!
Anyway, problem is very simple. You can manipulate an unit's flying height (even if it is ground unit) if you add and remove Crow Form (Medivh) ability from the unit. Just add and remove it immediately. When manipulating the unit's height, the unit doesn't have to have the ability. The fact that the unit had the ability even for a milisecond is enough to allow you to manipulate the height. Cheers!
~Daelin