I have done the topsy turvy that the cakes sit inside the other cakes. I love that style, because I can use the sps. I only use that system. That being said, I've been asked to make a wedge topsy turvy for a graduation cake. The wedge is covered in flowers, it will be a 6" round, 10" round and a 12" hex. with the wedge under the 6" and 10" the 12" will be flat on the board. My idea was using the sps, on 2 of the legs use say 7" legs and the other 2 use 4" legs. Where I use the taller legs is where the wedge goes. Also use chocolate to "glue" the cardboard to the sps plate. Do you think this would work or do you have any other suggestions. I really would like to stay with using the sps. I have had cakes crash using the dowels, I don't want to go back to that.
My idea was using the sps, on 2 of the legs use say 7" legs and the other 2 use 4" legs. Where I use the taller legs is where the wedge goes.
It won't work. There's no point in using legs that won't travel all the way through the cake that won't touch the base board which doesn't offer any support. (the 4" legs won't touch if 7" legs are also used on the same plate.) Plus, the top of the legs aren't cut at an angle to do what you're describing. Without the angled cut, the 7" legs would poke right out the side of the cake, and the 4" legs would also be forced into the cake at an angle... again, no support.
I'd suggest searching for some cut-away diagrams to view structure and support ideas.