Often the shape of the oval will make a differance. Ifer head is long and narrow and the hat openinf is shorter and fatter it ain't going to fit. (Some hats come in long over, regular oval and round oval besides size)
If ya don't understand size it is simply this. Take a measure of yer head, divide by Pi. That is yer hat size. Course the hat ain't round but that is neither here nor there.
The best option, have yer head measured for size and shape, then have the cutom hatter make ya on that fits in 100% beaver felt. I have one, got a very good price cause we were selling that brand at the time. I love it was a good investment, for me.
Cost, about the price of a good handgun. Do I want another, YES. Can I afford one, not at this time, maybe in a year or so.