Has anyone tried using these molds with buttercream as the base? I purchased my onlays and as very excited to use them but was having trouble removing my fondant from the mold without stretching it's shape. I was trying to put them on a buttercream cake I had and it was only "hacking" my buttercream (even though the cake was chilled). Does anyone have any tricks or tips I could use? I really want to use them but got a little frustrated when I tried decorating my cake. Took the wind right from under me.