Upon the arrival of some 4-40 inserts ordered from ACS, I used the previously drilled holes to locate them. I drilled the holes out to a press fit and inserted the inserts and then used the light cover to set the depth of the inserts. Once in place, I glued them in with CYA (later the back side will be reinforced with flox). The inserts were a little tall and fat to fit the light base, so I had to carefully file the base to fit before installing it along with the cover and lens.