If it was me I would draw a chalk line down the center, using the sewn seams as me guide. Then using it as my 'center' measure the 'width' you want, divided by 2. So if you want your braid to be a total of 9" half would be 4.5, using your center line cut at 4.5, flip braid around and then do the other side at 4.5. Because of the length and so many seams, I do not think I would try to fold the braid and cut.
good luck
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