and each has merits. In my method, the annulus of thickened epoxy is bonded both to the inner skin and underneath the outer skin. For a 5/16-18 you would use something like a 1/2 OD tube. That has about 1.5 sq in surface area if the core is 1" thick. If we believe West's literature (shear fatigue strength listed as 10,600 psi for 100,000 cycles), that should give you about 15,000 lbs shear strength. Way more than the bolt's tensile yield of about 2500 lbs. You can decore as far back as you want to get a larger area bonded to the skins. In the pictures, the decored areas actually intersected making a large area.

http://www.westsystem.com/ss/assets/Product-Data-PDFs/TDS%20105_205.pdf

In your method you have SS threads and perhaps a larger area of laminate involved, with the drawback that a larger hole has to be drilled in the outer skin. In this method you are also depending on the shear strength of the material at the perimeter of the washer.

In both cases it is likely that the bolt will fail first.