My make http://www.thingiverse.com/make:177764
-Very difficult to separate the parts for the first time. You will need: lubricant and knife.
-Poor gravity center, I think that you can improve this with other models. For example, I think that it is more stronger and balanced http://www.thingiverse.com/thing:711725
-To easy to do.
-Very good thinking by designer.