Something like that?
http://img824.imageshack.us/i/screen...040210281.jpg/
http://img146.imageshack.us/i/screen...040210301.jpg/
The whole Map on the Screenshots for my Mission "Wolfsjagd" (it's in German... my english is not good enough for a mission...) took me about a week to move into the right "heights"
The Blocks are the right idea, but you have to adjust every component to the right Y Position.
The Foundry takes always the Y0 for the height of something so even if a building like in the pictures is only a few metres besides another, and the ground beneath the "Structure Block" is only a tiny different you will have to adjust the height...
a
lot
of
times
Believe me it is real work, a lot of loading and exiting the map but it is worth the while in my opinion.
Greetings
Rev