Hollow Abraham

Fixed to allow printing completely hollow - fixed base to br flat top
and added infill density modifiers for both base and head.

For example of use with Slic3r see AMF file (optimised for 0.4 nozzle).
Three perimeters minimum recommended - with less you may get some holes on the shoulders (though it's ok if you plan to paint the model with thick paint).

Also decimated the model a bit to reduce polygon count and allow easier handling/faster slicing.