ooh ooh! I can answer this one! I just made my biggest cake project to date (4 cakes for a 100th birthday party). My biggest cake was a 14" round. I used a combination of things and got a fabulous 14"x4" cake.
Wilton Bake Even Strips.
3 metal flower nails in each 14"x2" cake pan
A homemade version of Wilton's Cake Release.
Parchment on the bottom of the pan
Parchment collar around the inside of the pan. [Go to Mikel79's fabulous tutorial for this technique:
Wilton 14"x2" round pans
Baked at 325 degrees.
I also successfully (for the 1st time!) torted the layers, created a SUPER-STIFF buttercream dam, and was able to end up with 1" of cake, 1/4" of filling, 1" of cake, 1/4" of filling, etc.
Here's a link to a thread where I showed how I achieved the torting: