I want to do a rope detail similar to the middle tier of this cake, except the cake will be in buttercream, not fondant. My question is, will the fondant rope be too heavy for the buttercream? Would I need to support the rope underneath with toothpicks or something else to prevent it from sliding? It will have a short drive to transport..that's the part I'm worried about!!

Thanks for your help!

I have put fondant on b'cream and not been a problem.  Just be sure your ropes are on the thin side.  Remember you are twisting together 2 pieces so make each one thinner than you think they should be.  Once put together they will look good :)Do you have time to do a small practice one?  Just  make your rope, put it on an iced cake pan or styro so it's on the side and see how it holds up overnight. (Or somesuch time frame.)

I think it would be to heavy for buttercream unless you support it with toothpicks or something all the way around. could you do something like that in stiff buttercream instead?