Shoot Anamorphic with a Clamp?
Here is a Philip Bloom Meet Up in Key West where they spent the day shooting Anamorphic, with an anamorphic clamp. I don't think this video looks that great, but Im not sure if its the clamp or the lenses they used in the clamp.
The Anamorphic Clamp available for $75 USD at vid-atlantic.com/anamorphic
I guess what the clamp allows you to do is mount anamorphic lenses to the 5D and lock in proper horizontal and vertical alignment.