The Sewforless is good price wise - no shipping and handling is a good deal. They are the same price as Accuquilt, unless you want the points that the Accuquilt website gives you. I have not sewn the clamshell - I saw a "Simply Quilt" show where one person used a template that she used to turn the curve. She did it also with pedals of the dresden plate. She sewed the edges (much like she was making a yo-yo) then put the template on the underneath side, pulled the string to gather the fabric and make it cover over the template, at which time she ironed it. Can't remember if she starched it or not, but it certainly gave a smooth turn. (Hope that makes sense.) There is also a video on You Tube by Accuquilt on how to sew them together. It doesn't look difficult, but again I have not tried it yet.