What is the obsession with "forming" carpet? If you have a custom car, you can't find "formed" carpet for it anyway. If you have a high trans tunnel, do the tunnel separately and bump the rest of the carpet up to the tunnel. It will look like it's formed to fit your vehicle. New carpet is harder to form than the carpet that used to be used in cars. The formability depends on the carpet's backing.
No one lives forever, the trick is creating something that will.