I don't have a backrest and only use the connections when I put on the luggage rack and box. The rest of the time I have 4 stainless button-head screws in the holes. Don't look too bad to me.
Sorry for the crappy picture but I think you'll get the idea. I have standoffs and long bolts that I use when I mount the plate that holds my pizza box. But I didn't like the bare bosses or the water getting down in them.
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I'd think the stainless bolts might look even better with white paint. (I'm not a shiny sparkle guy)