I collect hat pins from towns I go through and pin them on the van curtain. Don't take up any space.
I do also carry 3 hats with me.

There was a restaurant in Darlinghurst (Sydney) a group of us called "The Hat Place" because there were hundreds of hats hanging on the walls - all kinds, mostly from op shops - old fashioned lady's hats, school hats, cowboy hats, wedding veils, straw hats, etc, etc. After a few drinks (just one for me) everybody chose a hat and behaved in character (usually outrageous), providing great entertainment all night. There was lots of hat swapping amongst the patrons as well. Hats are like glasses in that, if you're used to always seeing a person wearing a particular hat or pair of glasses, it's a shock to see them without.