I look at it like this. If it was intended to be “supertight” it wouldnt have a pan head machine screw.! It would have a different type fastner. Sure it should snug up fairly tight and if its not the slide on the L bracket has wear, screws to long, or holes not drilled and tapped deep enough. Add a washer and go on. Your only gna get it so tight using a phllips head screw driver.