Hi Burr, 
> That looks very cool Michael. What happens on trimmed curved surfaces?
 
It can depend on the shape, there can be difficulties in the offset calculations in a lot of cases. Also currently the pieces being inset must be bounded on all sides by sharp corners.
 
But there are a lot of trimmed curved surfaces that will work as well, like here is a sweep that has a hole booleaned out from it:
  
 
 
    - Michael  
 |