Just remember slot 0 is the top slot. You should use the slot tag only for unspoiled nodes, i would imagine. Unspoiled nodes always have the same items in the same spots, as far as i know. You shouldn't have any issue as long as you find the correct slot (Using a site like FFXIVClock for instance, to find the slots is fine, just remember THEIR count probably starts at 1, ours is 0, so if they say slot 4, the tag should read <Slot>3</Slot>)