We are making our own wedding cake. It will be three tiers with a forth styrofoam dummy layer. The layers are square 6", 10", 14", and 18" layers. We will be using the SPS system to support the cake. Will the styrofoam layer be strong enough to support the cake on its own, or should we insert the legs into the dummy cake as well? If we do not need to insert the legs into the dummy layer should we still use the 14" seperator plate on top of the 18" layer to distribute the weight of the cake above it? Any tips or suggestions would be greatly appreciated!

Yes your dummy will hold up the rest of the cake, just put a board under the 14 inch. Something solid so that the legs wont push into the stryo dummy from the weight of the cake.