I was sick of tossing my coat and dry cleaning on the back seat so I designed this hook to wrap around the roll bar padding which is just about 3" diameter. It hinges open to slide around the padded roll bar, then when something's hanging from the hook it's locked closed and can't fall off.
The hinge at top is sized for a 6mm bolt, but use whatever fits.
I bumped the infill just knowing these parts would be load bearing. I don't know how much is sufficient.