Stress and calibration cube

Hey so I wanted something that I could use to test/calibrate my printer, and the normal 20mm cube seemed like a waste to me. So Here's my take on a 20mm, with a few extra features :)

Would love feedback or recommendations on how to throw more tests into this cube to make it a better all round test of the printer.

Built in OnShape:
Specs:
*40mm * 40mm * 40mm (outer)*
*Pipes and Square are 20mm internal.*
*Chamfers are 5mm.*