Been there done that but with a different pattern. I read in a Bargello book that reversing sides from which you sew your strips will eliminate the curves. As for your pickle, I would press the hack out of your finished pieces, pin them together, sew and then press some more. That is what I did. Maybe not the proper way to do it but it worked. Good luck. Also, I became very fond of spray starch. I over starch everything because it helps me manouver strips and reduce curves. Again probably not the proper way of doing it but I go with what works for me.