I don't want to wrap the post on my lovely custom Gunnar with tape - just vanity I suppose I only intend to use the rack when I am actually commuting or need it for other things, so most of the time it won't be there.

There isn't much of a space, and I tightened the bolts so tight that the sleeve I used is still attached to it after I removed it from the bike - so I know it wasn't a problem of it not being tight enough. It isn't much space...I wonder if a thin rubber sleeve would work - assuming I can find such a thing? It would have the added benefit of protecting the post from being marked by the rack. I think a washer might be too thick but I could be mistaken.