I just purchased the Bebob Foxi and want to mount it on the 15mm rails. Instead of the original spacer bracket that is pictured in the instructions, it came with another metal piece that can slide onto one side of the 15mm rod and somehow serves as the mount. I have no idea how to mount the foxi using this thing. Can anyone walk me through this process who has the same thing and knows how to mount it on the rails? Thanks