I am about to carve a skateboard ramp cake for 20 people. I figure it really doesn't have to be that large for that many people, but I do think I will need 4 cakes high (2 layers each) to get the slope. I was thining of a 1/4 sheetpan (12x9) for the cake, or 1/2 sheet and cut to that size and then carve the slope. Any help on if this is actually enough? Do I need to dowel if it is only 3 layers? 4?