Though this is an older thread, this might still help some people...
I just installed a map of Sardinia (Italy) for use with GDAK in offline mode. Copied the Sardegna_L.map from OpenAndroMaps into the GDAK directory and selected "MapsForge (offline)" from the menu - works, but does NOT show the contour lines...
Here's the trick: download the Elevate4.zip map style from OpenAndroMaps. Put all files in that zip into the same directory the map is located in (or you might use a subdir like "Elevate", for instance). Then in the GDAK menu "Map settings", tap "Map theme" and select "external". In the following file chooser, navigate to the Elevate.xml file and select that one. Now just exit all menus - and voilá, you got contours as well.
Just keep in mind that resizing that display needs quite a lot of processing power which means you will want to have your charged power bank available in the field as well
Happy hunting,
Marco