Rubik's Cube 4x4 centre piece

I designed this piece to replace a few that were broken in my original Rubik's Cube 4x4x4. The design has changed since then, so the STL might be of limited value.

The scad shows the measurements I've made from a few well-worn pieces, and how it was designed.

The piece works out well, although my level of knowledge of 3D printing has allowed the thin inner section to be more brittle than it needs to be.

I haven't designed any of the other pieces that make up this cube, because none of