I can't say how critical it is - But how are you mounting to the 80/20? Drilling into the 80/20 itself? I built (well - hired it out) a set of drilled and tapped rails to slide inside the 80/20 slots and then screwed the thk rail to that. Worked sweat as -- for making parallel adjustments - and I can always reuse the 80/20 as its not full of holes!
Does that help? BTW I did every other hole when I installed the rail - but my longest piece is only 36 inches. AND I do check it every so oftenm to make sure the bolts are tight - guess one day I'll usre that LockTite I bought too.