For through bolted fittings that pass through soft core
like foam or balsa, best to rout out the core around the fastener, fill with thickened epoxy and then redrill the hole. I use a Dremel 199 bit to do the routing out, use a syringe to pump in straight epoxy resin to thoroughly wet out area then suck out as much of the resin as I can with the syringe, add in the West 404 filler and squirt it back into the hole. Redrill the hole and counter sink so there is a sealant pool at the top of the puka. If I'm careful, the fitting hides the fix. Use good sticky duct tape to seal the bottom of the puka so the resin doesn't run all over. Masking tape won't hold and epoxy is a bitch to clean up off a teak
and holly sole. If there is a liner so you can't get at the bottom of the puka to seal it, have been told that construction foam sealant, the kind that actually gets hard, squirted into the hole before you rout out the core works to seal the bottom.
If you are talking self tapping or sheet metal screws, they will eventually hog out the hole and no longer hold if unscrewed and rescrewed a few times.. Should only be used for non structural hardware
as the fasteners will pull out if subjected to cyclic shear loads. Won't hold at all if used in matt/chopper gun layups like cabin
liners sometimes are made of. If you do have a fasteners that is screwed into the layup
and strips out, fill the hole with epoxy resin, maybe with a bit of 404 added, and redrill the hole.