Well, Mr. Monkey, that can be solved with this:
this setpos [getpos this select 0, getpos this select 1, x]
x = the height of the object/building, you really need to use trial and error to get it right.
EX:
this setpos [getpos this select 0, getpos this select 1, 24.5]
is the height for the 2 tall towers in Petrovice on Nogovo
hope that helps.