Tall Reversed-S Custom

W2 (Width2) represents the withdrawn front part
W3 (WIDTH3) is the slope width.

Each radius RAD [1] & RAD [2] may be redefined.
Image below represents default "S" radius (D-D2)/2:

When SD1 (Shelf Depth 1) is different from SD2 (Shelf Depth 2), 20-20 uses only SD2 and repeats front curve (behind frame).