if i don't use a thin batt in my table toppers i use an extra layer of fabric (usually white flannel) in them. i made a table cloth without anything in the center one time...and just really feel like they need a little more body than that so i put something inside. it depends on how much piecing is in the top though. i've found if it is a project with LOTS of blocks/seams/little pieces i use either a batt or flannel...it helps to make those seams not show through on the back but if it has large plain squares...not many seams then it's not so necessary. i did make my mom a runner i used warm & natural in and she was unhappy when she washed it...it was too much batting...puffed up like we love in quilts. a thin poly works better.