These base components are meant to be a drop-in replacement for base.stl from the original Portabee source code. I've built the base from scratch in OpenSCAD using the original as a reference.
Please refer to the posts I've put up previously on how I've used these components in my Portabee rebuild. These can be found here: http://www.igorkromin.net/index.php/2015/03/03/rebuilding-the-portabee-3d-printer-part-1/.
The STL and SCAD files for the new base components are on Thingiverse and can be downloaded here: http://www.thingiverse.com/thing:728089.
The original Portabee documentation and source code can be found here: http://portabee3dprinter.com/support/portabee-kit-docs/#k7.