It is important to have everything properly ironed, nut even so, even twin seems a bit wonky to me. Usually this is a technique I use for lap/baby quilts. Lately, when I have sewn top to back and turned it right side out, I "play tug of war" with DH, pulling it every which way.This seems to get everything properly lined up. For a 42x65 quilt, I generally leave about 8-10" for the birthing.