Here's what I ended up doing. Found some burlap-type ribbon (WalMart). Covered the back of the ribbon with some buttercream. Wrapped the fondant-covered tier with the burlap ribbon. Wrapped and tied the (real) raffia around the burlap. That way, nothing non-edible/non-food-grade was touching the cake. Worked pretty well, and the burlap ribbon actually helped hold the cake together, as it was in a hot, non-air-conditioned barn! Hope that helps a tad!