My tailgate supports just arrived today - the rods look to be about 5/16" diameter. I had thought about maybe making some out of flat bar stock but was unsure of what to do with the ends.

The first picture shows what they look like on the truck:



The next four show the length of the supports from the ends and the middle hinge area.













This final picture shows the two different ends:




Hope these help inspire someone to make their own supports. I'd really like to see what people come up with. I had thought about just using covered chains but it doesn't look like there's enough room.