If you iron polyester blends with a really hot iron you can watch the fabric shrink 1/4" right before your eyes... I just did that the 3rd week of January. Our niece was due with her baby boy and last minute my sister decided to make a baby quilt.
I told her about the D4P being a quick block to sew, so she sewed the 4-Patches, then passed the blocks to me to finish, and I passed them back to her to sew the top together. She used some poly/cotton blends. It wasn't fun. Even though I was really careful with a low setting on my iron, I ended up trimming them down to 8" because the polyester disappeared and there was no seam allowance.