My samples include
1) a variegated #5 perle, first done in a straight line, then I tried to do two scallops.
2) Next, I used Soy Luster in a line, then back to back.
3) I tried a Needle Necessities thread 50/50 cotton/rayon, but I think the knots look sloppy because of twist of the thread.
4) Finally, I tried #8 perle cotton in a straight line, then tightly packed. The tight stitches lose the definition of the stitch.