For 3/16 fasteners (and smaller) glue in an appropriate length of fiberglass
arrow stock, sand it flush when the epoxy cures and do your lay up over it.
Drill out when the lay up cures.

Arrow stock is (should be) available at a sporting goods store. I've even
seen what I think is graphite arrow stock which might work even better.

I used this method (in my early 235) in quite a number of places where the
stresses have to be high (gear door attach for instance) and have never had
a problem with it in 12 years of flying my Lancair.

Dan Schaefer