Today, I drilled out all the lightening holes in the main spar using hole saws I bought from Lowes. The main spar predominantly has 5 inch diameter holes but there is one hole at the wing root that is 4 inches in diameter and a hole near the center splice that is 4.5 inches in diameter.

I also used my files to file out the main strut attachment bracket pass through so that there is clearance for the strut attachment bracket to pass through without rubbing on the spar web.