How do I make this megaphone cake?!!?

http://www.flickr.com/photos/humbertadventures/2605666217/

It's KILLING me that I can't figure it out!
All I can think of is making multiple different-sized round cakes, trimming different portions off the ends, stacking, doweling, then laying them flat. That seems like WAY too much work & waste.
Any thoughts?!?!
THANKS!
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I'd make sheet cakes, stack two or 3 layers, depending on how high you want to go, then trim it to shape. You could make a template for the angle shape and cut that away first, then just round the edges down.