Has this been made yet? My searching skills are quite poor, and I'm not quite sure how to word it...
Is it possible to make a concave 4x4F/2x2F corners?
^These are just an example I came up with...^

It would make building things like these a lot easier for me, and maybe a few of you.
EDIT: Forgot about an example on what it looks like...
This was built within Valve's Hammer Editor.
*FIXED IMAGES* somehow they broke lol...