I installed mine using the plastic as backing. Be sure you cut the screws down some or they may damage your car. On a 98 E-300, they will damage the plastic cooling fins when the hood is shut. Leave the nuts on, cut them in half, then back off the nuts to act as a thread chaser. I used blue Loctite
to help keep them secured.
Sure would like to add that "Mercedes Shop Forum" badge that had me salivating earlier this year...
Cheers