For a primer on hard points and pylons, see www.bvmjets.com.
The Bandit ARF section shows a drawing for tank and pylon construction and installation.

On the drawing, pay particular attention to the hardwood dowel relationship to the wing spars and ribs.

I think that it is wise to distribute the flight loads from the dowels to the spars. As long as the dowel locations are correct, and the skins are thick enough, there should be no need for an external skin doubler.