Beautiful quilt!
I must be the only person in the country who does not use a walking foot. I like to use spray basting but the last two quilts were full bed size so I used the classroom tables at my LQS - could not use spray there. I use a larger size safety pins. I use the open toe embroidery foot on my Designer I and s l o w d o w n, smoothing things as a sew. So far it all works fine and no problems with puckers on the back. Also, I start in the middle and work my way out. I usually do an outline stitch design to highlight the main block design.