Easter Island Head

My father and I enjoy the Easter Island Head song. https://www.youtube.com/watch?v=ibiS26Tky40

So for Father's day I wanted to make him some 3d printed stone heads. http://www.instructables.com/id/3D-Printed-Stone-Head/

My design is modified from http://www.thingiverse.com/thing:144668 to make a space in the back for a nail staking it into a garden. The slit is ~13mm wide if memory serves me correctly.