My father is into archery and so when he lost a quick connect for his v bar, I set out to try to print one for him. The metal original measured 12x19 mm with a hole size of 8 mm. When printed using these measurements it was slightly too big, so I adjusted it. Now it measures 11.5x19 with a hole diameter of 7 mm to allow the 8 mm screw to cut it's own grooves. I'm planning on adding a customizable version, but first I need to learn how to use SCAD.
25% infill seems to work fine but higher is probably better.
Measured the original using a caliper and then adjusted some measurements too allow for better tolerances (when printed with measured sizes it was slightly too big)