I have done my GD's names on the front of their quilts in the border with FMQ. However, after reading the posts, I'm thinking that you may want to use some kind of pellon. Maybe the light-weight one that you could leave in or try the tear-away kind. I did not use any but I believe it would be helpful especially if you use more that one pass over the letters. You may also want to starch the fabric too. You could use a small zig zag over the letters but I would think you would really need some stiffening in order to get it to lay flat. Practice on a scrap piece of the fabric with different backings and see what happens. I really love the idea and would hate to see you get in a bind on the quilt itself. Not easy getting those stitches out. Good luck and please let us see your finished project.