Yes, I think the bigger supported area under the arm (in your case the width of the arm and the L) the more support it will create for the swing out. Just like creating a wider more stable base. What if you moved the latch behind the plate and put it on the "L" piece, so it was protected and not hanging off the face of the bumper? Could you mount the hooks on the step of the bumper and still open the tailgate? Or maybe make it really trick and recess them lol.
I'm still working on some small details. Like trying a rotary latch setup.. although think about this.... I realised this after I did it. On my bumper i push the swing Arms in to give over the bumper and not flush with the face like most. For two reasons, we'll maybe more . Lol but initially to clear for possibly putting recovery pockets like my front bumper. And second I think it looks much better! Less blocky and cleaner. Plus it give a small step if you have little feet. Just kidding.
So on to what I noticed by doing this and using the destaco for this bumper. I had to come back out to the face for the latch. To do that i added another piece of tubing. Then capped it with the latch and stop plate . So the arm is now L shaped. This helps brace against the twisting force caused by the tire mount that all Arms see. It puts the end of the tube closer to the centerline of the tire and creates leverage. I dont know its late im tired but i think its doing something.lol. Under the arm is a machined piece of delrin that presses against the top of the bumper when clamped. And the bumper stop is poly not rubber. The rubber gives after a while. This set up should last and stay tight!