If you do a pieced top for it, I think I would line the pieced part with a sheet or muslin to help make it slide on and off the comforter more easily. Also to keep those seams flat. If the back has only one or two pieces for it, I would probably not line it - but if there are seams in the back, I would either use wide seams or overcast/serge a seam that is 1/2 inch or less.