I press open a lot when it makes less bulk in a seam. And I always stitch using a very short stitch length. Last year I found 100% cotton thread in 60 weight thread and now I use it exclusively in piecing. I am using my old 50 weight thread only in borders and attaching binding just to use it up. The finer thread adds less bulk to seams. You would be surprised how much thread adds bulk to a seam. It is called Presencia and I get it online from Red Rock Threads. You do need a o be careful when ordering as it is available in other weights as well.