Here is something I'm currectly working on...
http://mysticj.fileave.com/Photo0382.jpg
http://mysticj.fileave.com/Photo0383.jpg
I know it's not pretty. Using a dremel to merge the short and long runners while increasing the size of the plenum.
http://mysticj.fileave.com/Photo0391.jpg
http://mysticj.fileave.com/Photo0392.jpg
http://mysticj.fileave.com/Photo0393.jpg