Duplo Compatible 4x2x2

After seeing Cunicode's brilliant brick:
http://www.thingiverse.com/thing:28240
Which was inspired by http://www.thingiverse.com/uck

I figured my sons Duplos need something similar :-)

WARNING:
Children are dangerous!
Erhm, I mean:
DO NOT LET KIDS PLAY WITH THIS UNATTENDED!
Parts could break off, they might swallow or choke on it, etc.
Allow use only UNDER CLOSE SUPERVISION.

UPDATE: Added a revised file with tighter fit on the bottom.