Want to make sure your screws are tight? Now you only need one 3mm Allen key
I typically use M3 screws and bolts for everything. I also LOVE captive nuts. At least that's what I think you call it when model itself takes care of holding the nut for you.
Needs 6XM3 nuts (lock nuts preferred) and 6XM3 20mm screws
So use your existing hardware and avoid yelling at a little tiny nut that keeps slipping. YAY :)
Then print all parts at ~80% infill maybe .25mm layer height?