Check the import options in DM, I think it defaults to surfaces for some formats. The sliding mesh approach is sensible, but I've found it better to rotate the outer region so when post processing you keep the "building" orientation constant.
One comment, carefully check your definitions for map/grid north, true north, magnetic north and similarly for the wind rose. You'd be surprised how many variations you'll find.....
You are navigating away from the AIS Discovery experience