The old Harley Extra was built in 1988 with a single dowel, if it can put up with my flying and still be tight after all these years I would say it holds up pretty well. I use two 4-40s or 8-32 hex heads to hold my wing on. Never once come loose. I have a 1/8 ply sheet/block on top of the wing and fender washers under the screws. Oh, they also screw into blind nuts. Why it has never vibrated loose I haven't a clue but they hold very well.