Get some play doh and put it on the inside of your fairing about where the slider goes.
put in just the bolt and leave it sticking out
install the fairings, press on the play doh a little to get a good impression, then remove them carefully to not mess up the playdoh.
then drill a pilot hole in the very middle of the bolt head impression on the play doh.
drill the hole for the frame slider using a hole saw, using the pilot hole. use masking tape on both sides to keep it nicer.