I needed to have a solid box for a motor, so i could leverage an additional, customizeable general purpose box. It contains two U shaped parts, which are very easy to print. Make sure it looks like an "U"when printed so the weak print layer direction becomes uncritical.. When assembled and tightened with screws, the box becomes very robust. To use it for your purpose, take the original openscad code , cut out the required openings and compile it. One piece requires very little support, so make sure its turned on.

This thing is developped with OpenSCAD - Python Editon. Find a summary of the all the adavances fetures in http://www.guenther-sohler.net/openscad/