right you are about the scant quarter inch sewing and cutting. I guess the whole idea is patience. I do not have a lot of that............so I just keep on trying.

I gave up trying to make hst the perfect size. I now make them a bit larger than required, then trim back to the right size. I regret that I'm unable to do it right the first time, but we do what we have to do.

Be sure your seam doesn't veer at the ends. I press my seams open and that has helped me get exact size.