I will be honest...I NEVER bake cakes higher than 325 F, because I've found that they tend to dry out. Baking longer at a lower temp will definitely help. As for wetting a towel and wrapping around, you can always use pins to hold the towel on, but you do run the risk of the towel drying out and causing a fire.

What size are the bowls? And as for stacking...your best bet to keep the cake from sinking is your support, not the cake itself. Looking at the picture, you'll want to cut the top of the bottom shape to get a flat surface for the next layer to sit on. Make sure to put dowel rods in the bottom, and use a plate or cardboard circle for cakes under the top layer. Once the top layer is placed on the bottom, you can use one sharpened dowel rod down the middle of both to secure the top layer to the bottom.
If you don't use a cardboard circle, but rather a plate or something that a sharpened dowel rod won't go through, you might be able to get away without the center dowel, especially if you're not transporting the cake.
If you have any specifics on support structure, etc., feel free to PM me. I have a side cake-decorating business, so I do know quite a bit about it.
