The spacers are for if you are mounting the cupholder on an almost, but not quite vertical (or horizontal) surface. As to getting to the lower holes for vertical mounting, I (sort of) simply disassembled the flip-down-snap open innards and was able to get a long screwdriver to put the screws in (I used self tapping screws so I didn't need to drill through the cupholder because the screw did it for me). After I got it mounted I just put the innards back in it. If you want, I'll send pics of my cupholders and point out what I disconnected.

Sean B.
'90 V'gon, "Happy Bus"