2017 cx-5 ... coilpack screw into ???

Replaced my plugs after 72K. Put coil packs back on plugs and one of the screws crossthreads and while its holding fine, I am concerned for next set...
Do the coil packs fasten to valve cover or to valve-head body?
 
FYI- The valve cover has brass inserts that the coilpacks fasten to. So at least its under $300 for new valve cover kit (includes gasket).
 
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