Try wheat germ or wheat bran. Wheat bran needs to be sieved to get out the big bits and can leave a ring inside the shoulder - well at least I have seen it once or twice. The wheat germ is oily and doesn't seem to do this and is a bit lighter and springier and easier to get into the case. It also doesn't seem to harbour as many bugs that eat it and make silk balls in it like wheat germ does - wheat germ is best baked to dry it and kill the bugs.