I was looking through some builds for frame rails and noticed some areas where the frame rails would (or could) be drilled completely through to make it appear to lighten the frame. That technique has been used in everything from racing to zeppelin structures. I have a few questions, though. I've heard there is a formula for the diameter of the hole related to the frame rail height as well as the distance between centers. This is supposed to be based on shear strength of the material and the stress paths around the hole openings. Anyone know for sure? The second question I have is that if you pop enough holes in the frame, what's the best way to finish them off without sleeving them and adding the weight you just took out? Any thoughts?