For the first time since I have owned the coach, the rear hatch didn't stay camed over when I opened it today. maybe I haven't opened it when it was cold before or the struts have lost their pressure. I haver new struts and will install them tomorrow but I wanted to keep on going with the bed actuator project. I drilled a hole through the two ears on the door and installed a safety device to keep on going. It might be prudent to use it even when I put the new struts on as possible wind gust might dislodge it. You can buy this type of pin at the big box hardware stores.
That looks simple and effective. It would only take it falling down once while servicing the coach to make you wish you had done something like this.
Like your idea. . . A single large carabiner over the hinge can also prevent the door from falling and breaking the back of a person leaning in on engine.