this is my 2 cents....I realize lots of folks do this and if it is your choice, fine...but I never press a seam into a bias strip... if each of your seams is not perfect, then the crease will not be in the right place, but if you leave it uncreased, it will fold perfectly as you 'get to it'.... I also prefer double chanel strips as they 'correct' themselves when you match up the two raw edges, the tendency to scoot forward is counteracted by the two edges which correct for each other...