Perfect Cubed Cube Frame 41-20-1

This is the first of two Perfect Cubed Cube Frames of order 20 and size 41 (the minimum size):

       17             6             18
             10                 11
                  14 15 12
        3         8         9         7
                  19  2  20
              1                   5
       21             4              16
 
There exists an isomer of this. (same elements but differently arranged)
Perfect Cubed Cube Frame 43-19-1 is slightly larger, but has only 19 elements.