I've only used wool jersey and flannel for covers. But my favorite fabric store has some gorgeous blends that I'm wondering about. They have a 75% wool 25% cashmere and a 75% silk and 25% wool blend. I'm thinking the silk/wool may not work since there isn't enough wool content. I'm not sure about the cashmere though. It sounds delicious, but I really don't want to spend $12 a yd to find out it doesn't work! Has anyone tried a blend?