Summary

Repair parts for broken/crumbled GameCube screw posts. Trim existing broken screw posts if they were jagged when they broke, adjust replacement post and flange lengths (you want the flange longer than the inner post, so you can join it to the existing post), and use to extend the broken posts back to their original height. Original screw should self tap down the centre.

The front posts should sit 1in high from the lateral 'bar' near their base, and the rear posts should sit about 1 7/16in from the smallest of the little protusions near their base. You might need to print a few test runs to get it just right while you tweak the sizes.

They fit snugly inside the recessed posts where the carry handle is, or just slide over the front posts, as seen in the photos. Should be a friction fit, but you might need some extra sanding or work with a craft knife to get them just right, depending on your printer and settings.

And you might want to colour match your filament with your GameCube shell, which I didn't, as you can see.