Like Dwight, I use #346 on top. I also use #277 in the bobbin as that combination pulls my stitches up consistently the way I like to see them. I wouldn't go lighter than #277 on top, but again, most of this is personal preference. Double rows of stitching is fine, but the primary row closest to the gun is the important one. The outside row is strictly aesthetic. I like my stitch length to be somewhere the 6 to 6.5 SPI range. Stitch lengths in the neighborhood of 5 SPI look too mass-produced/unrefined in my view, but most of this is my own obsessive/compulsive way of looking at things.