Box with Honeycomb cut-outs

I created the stl file in the windows 10 3d builder program by subtracting from the box a sheet of hexagons that I'd created in scad. The simple box file is included as well.
I've now written an scad file that produces the equivalent box and should be customisable.

I've printed this ok with no supports.
I've printed the stl file uploaded here and an stl file produced from the scad file. I use simplify 3d for slicing and got best results by making sure that "Apply bridging settings to peri