Quoted from vid1900:Enlarge the pop nail holes so the heads are not proud of the playfield
https://pinside.com/pinball/forum/topic/future-spa-hardtop-install-vid-s-guide#post-5910342
This! Tapping them on top of the hardtop could create an issue wit the stress of the had being pushed down over a void. Just widen the hole so they are flush. May be a good idea to fill the beveled holes(toothpick in the middle) then install the mounts as directed.