Actually Wick, I had done the same with the helmet shown, but the leather was too thick and therefore the helmet was a bit tight, so I went with a cloth pad over the leather edge and a cloth liner for the best fit. Poorly fitted leather helmets are quite painful so I needed to do something.
I used spring clamps for Lowes to hold it all together while I sew it. I used a stitching wheel from Tandy Leather/Leather Unlimited to get the stitching even and drilled holes in the leather to ease the sewing. This was not needed in a cocked hat as a sharp awl easily made holes in the felt.
CS