Getting an 18" OBR, it will sport a Conquest 4.5-14x44 with Z800 reticle plus a scope-mounted Aimpoint Micro. Don't really know if I need an additional set of backup irons, but in the interest of having full backup in case both of the other optics fail, what would you suggest?

Obviously I want something low enough in the rear so that the scope can clear it. Are there any specific "308" BUIS setups? I was considering the MATECH 600 meter BUIS or KAC Micro 200-600, but would the 200-600 meter settings not match up to the .308 cartridge, and with the LaRue scope mount and scope, would it clear?