I've finally found a good, simple and very cheap cargo door strut that works like a champ on the forward cargo door of my RV8. I found a local marine shop and purchased a boat hatch strut that's comprised of an 8 1/2inch spring with mounts on either end that are perfectly suited to the RV8 mounting surfaces. I secured the bottom mount 6 inches outboard of the hinge (using screws and metal lock nuts) then pop-riveted the top to the door itself as seen in the photos. The only mistake I made was using a Sharpie to mark the holes on the door: I decided to have the door open a full 90deg so I made new markings and took the paint off the inside of the door where I tried removing the old markings. You can have the door open as narrow or wide as you'd like depending on where you pop-rivet to the door. With the door open, the spring is fully extended and will hold the door securely open, even in high winds. To close you simply push on the spring to collapse it and it tucks nicely inside the compartment. You can probably find these spring struts at most any Marine Store. I got mine at a local Mom & Pop shop and the guy will be happy to ship to your door for a mere $18 total cost (Richard Sewell, 770-253-7996). Ask him for the airplane door strut he sold to Trapper. Note that I'm not trying to advertise here and am not profiting from this but am just providing a source if you can't find one on your own.
BTW: A link to the photos is posted below--I couldn't get them to come up otherwise. Be sure to use the arrows to pan through all of them as necessary: