Hi fhoofman,
Yes I discovered that one, while I was constructing a very old building, with walls that needed to be 40cm thick (try that wall thickness and see what happens to your door!
) the only size that works for the open doors at the moment is, Emmanuel's original 7.5cm for walls (It's okay Emmanuel, your secret for not wanting to change the default wall thickness is safe with me! 
)fhoofman there are two workarounds, either export the door with frame and edit the frame thickness in a program like Art of Illusion then import it again, making sure to tick the door/window tick box while importing.
or
export the door and frame, remove all the frame leaving just the door, import the door as a normal obj, without ticking the door/window tick box. use an empty frame from the furniture list, then correctly position the imported door.
Personally I like the last option because the door can then be set open at whatever angle you like.
Hope this helps!
db4tech
