MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
If you have issues printing the core you can try like I did to flip it upside down, gives more surface to stick and the overhang angle is the same on both side so it wont change much. Also, if printing on blue tape try airspray, its the PLA equivalent to acetone/abs mix for abs printing.
FYI: FOR EVERYONE PRINTING THIS do not try to bend the shells by the tabs to fit it in the core, you will break it. (happened to me) Instead grab the sides on their entire lenght and bend very very slowly and not a half mm more than you need.