[Burgs]

If you drill the hole in the mounting base, larger,... you can then use the longer correct thread bolts, that you buy, and cut to the right length, because if they are too long, that's not good either,... then the mounting blocks will sit better to the windscreen posts, because the longer, cut to size bolts, can go thru them at an angle. Buy yourself a wire cutting pliers, that also cuts small bolts. Buy extra bolts so you can test cut different lengths until you get just the right length.

Or you can do what xlr8or said.

Bolts that are too long for the visors, if you install those too, will crack your windshield!