Gadzooks

Hi @Christiaan
 
You can provide an overlap through the roof element OIP
 

 
Enter a figure in the bound offset box (here I've used 100mm on a multi layer roof)
 

 
(not the best example roof, but shows layers are individually adjustable)
Hope that helps

Have you updated to SP2? It included a fix for this roof issue

Christiaan - (as you've probably decided by now) I don't think VW makes this a very easy process. It's certainly not explained anywhere I looked.
 
However - and someone please correct me if I'm talking ******. When you customise a workspace it saves to your User files rather than the VW application files. When you startup VW it looks to the user folders first.
 
I'd ditch that folder contents. By that I mean do it in a safe 'no harms been done' way by putting the files on the desktop for the moment. You can always put them back if this doesn't work.
 
Then restart VW.  
VW should warn you it can't find a customised workspace and suggest another. I believe if you've given it no choice other than to choose from the defaults you will find you're back to where you want to be. I've just tried this btw, and it worked for me. (And I've now put my custom ones back - without problem!!)
 
Note: Just as a check to this, look at the file creation dates on the workspaces that are in the Application folders. I believe you will find they have the same  (or very close) dates to the release dates of VW versions. Or - they might be modified and be similar to an SP date (where a later SP has released a small change to the workspace.)
 
Hope this works out.
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Edit - I should say do this whilst VW is not running - then startup (safer that way)