Lets talk hat sizes, as that is always a pia for me to mail order them. Some years back I had a hat maker tell me that my size was a 7 1/8 oval. Now days I find that very few hats will fit well based on hat sizes and just a little off seems to count a lot in comfort. Most often it does seem that the 7 1/8 or 7 1/4 are best but how do you handle mail order with this size variation and fit does vary from maker to maker? Is it better to go a bit large and try to tuck a filler inside or go small and try to steam stretch to a better fit? Is steam stretching the cheaper campaign hats even viable and how does one do it?
It's a problem. There is some variation between makers, and you will also find that hat size charts don't alway agree. Best is to take a careful measurement with a good cloth tape and let the maker select the size based on the measurement. That said, you must know whether you are a standard or long oval. Most quality hats will take a bit of stretching with no problem, provided you use a proper hat jack and go SLOWLY. Too fast and too much will break the stitching in the sweatband and deform the brim. I use a tea kettle to steam hats in order to reblock or stretch. Some folks spray the hat with distilled water, shape and let dry. It is important that the hat jack be left in place until the hat relaxes into the new size. With a campaign hat, you will need to steam the brim and have some way to hold in down flat and smooth, or you will get a swoop! Some of the folks who sell campaign hats also sell a form or carrier that keeps the brim squared away.
I once read an account of how Tom Mix ordered a new Stetson, and when it was delivered to his dressing room he was taking a shower. The fella that brought in the hat called to him that he would leave it, and Mix told him to bring it in. He did so, and Mix put it on his head and went on with his shower.
Here's a video of Roy Rogers showing how he blocked his hats. Note the running shower!