I wonder about departure angle? I just worry about it catching on something. I know it should be high enough but you never know. Also, my rack came loose in Moab last year too. I see your point.
I was at the junk yard a few months ago and was thinking the mount off the trooper door might work. I didnt even pay attention to the pattern or anything mostly looking into the mounting strength.
I really have thought about this. I use my door alot though cause my dog goes where I go usually. So I worry about the maine brackets.