This is Dyson 14 oz Poly and it is exactly as you describe. I did a new stitch that helped but I guess I just have to trust it to shrink up. Your right, you can not pull it tight like I did with the 8 oz Primo from skin boat school.

I just removed a couple of feet of stitching because of the way it looked. Decided to check for any answers. So, back we go and trust the heat will pull it tight!