I promised to post some pictures of how I am sewing the curves on my JN quilt. Keep in mind this is the very first time I've ever sewed curves, so there may be better ways to do it, but this seems to be working for me.
First picture - the two pieces that need to be sewn together. The top piece has a curved seam that has already been sewn, but not pressed. It will lay flat when pressed, but wanted to show that it isn't flat when first sewn.
Second picture - I match the center and the two ends of the two pieces and pin. The inner piece still has its paper, but I removed the paper from the outer curve. If the curve is longer I match more points on the curve by folding both parts into 1/4's to see where they should match up.
Third picture - stitching the two together along the line on the inner curve. You can see all the additional pins I put in before start to sew. They're about 1/2 inch apart. You may not need as many pins as I do.
Fourth picture - the end result of a different block after pressing.