One thing that helped me was making sure that I am pulling it taught (but not too taught!) in the same direction consistently. And I try to rotate the direction I thread the binding in as I move up (so I go up and out in one direction, and then down and out in another). I feel like that helps the binding be balanced.
I also found using a good linen thread is important for Coptic. It is not as vital on something like a pamphlet stitch.
Great work again - love the cover! :)
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