I've had a very similar idea brewing. I drew this up a few months ago, I've been rebuilding the truck, so this project isn't the highest priority. Once I drive it out of the garage in a week or two, I'll begin work on it.
My support bars would be ~82" long with the gusseted design you've shown, using 1" square tubing. After thinking about the drawing more, I do not think there will be such a harsh angle to the front of the vehicle on drivers side. I literally made a model out of coffee stirring straws and and half a stack of sticky notes cut to size. I found that with the shape and layout that you see above, I will have fewer moving parts, and most/all parts would be the same length. I'm considering making the canvas reversible, and adding a fourth arm on the passenger side so that I can flip the canvas over and it work on that side as well.... in case the camp site does not allow for the vehicle to turn around to properly position the coverage.
But, if I go to the extent of adding the third arm and flipping the canvas, I might as well have made the awning go 3/4 of the way around instead of the half shown above. But the other side of the coin is that I don't feel its necessary, and storage space is already at a premium. A canvas tarp that either size will take up a fair amount of room and only add to the weight.