Yeah, D'Oh! When I first looked at them I thought they might be Torx, but the slits plus some poor lighting made an optical illusion that made it look more like a standard allen. Found the right Torx and and got the bolts out just fine.
I also found the instructions for the RRO rack and rails .... after I finished installing the whole thing. D'Oh! It was hidden under some packing material. Not that the installation was really rocket science, but there were a few things on the instructions that would've saved me a bit of time and also kept me from scratching the powder coating with the U-bolts. Oh and the instructions also mention that they're Torx ... Sigh.
Overland 4x4 EcoDiesel, Deep Cherry/Light Frost, ORA-II, Adv Tech