Greg Wades extruder insert

Greg Wades extruder (for example http://www.thingiverse.com/thing:18379 ) have a hole at bottom for hotend
But my custom reprap have Geeetech buda extruder hotend (like this http://www.geeetech.com/reprap-hot-end-v20-with-035mm-04mm-nozzle-p-685.html )
So to connect one to another and retain the ability to install bowden extruder or another type of hotend
I'd make this removable insert.
openscad source included