A question. You don't mention a backing plate for the winch
. Do you have one, & if so, is it Bronze?
Obviously, they're not mandatory for every winch & application. Though they rarely (if ever) hurt. But if you do have one, then having all of your fasteners matching it adds an air of class to the boat. Ditto on simply having your washers match up with your bolts & nuts.
IMO, a shiny, well polished Bronze backing plate for winches, definitely adds to almost any boats belowdecks looks. And some Bronze backers (plates), can even be clear coated, in order to cut down on maintenance
Plus, if you like, with a backer of any thickness, you can simply tap it for the bolt threads. And then add acorn nuts, in order to remove the sharp(ish) points on the bolt ends. Thus negating the need for some of the fasteners which you're inquiring about.