Originally Posted by
davemillard
I had the same issue, and you would have to pull really hard to get it to be flat. I seem to have fixed mine: massage in some strop dressing front and back, and sort of form an opposite bow with the strop and pull down, mine was concave, so I "bent" it to form a convex shape, and pulled down the length of the strop. I did this a couple of times and it seems much flatter now. I had not been dressing the back side of the leather, and since it was hanging in the bathroom, that might have led to the problem or made it worse, so a little protection on the rough side might be the cure..
Since you have concave and convex, yours will be a little more difficult. Hard to put into words, hope it helps a little...good luck