A catalytic converter starts to work between 400-600 degrees Fahrenheit (204-316 Celsius) from some temperature tests i competed on my coil pack 1.0 for my dissertation i recorded
Front (Manifold) - 631 c
Middle (after downpipe) - 445 c
Rear (back box) - 215 c
The results show that it is possible to have a catalytic converter anywhere in the system but as you can see having one at the rear would be borderline .....
Was trying to see if you could use a catalytic converter as a silencer to get rid of the back box 
as on a rally car produced after 1999 you must have a catalytic converter fitted i thought about making it a multipurpose piece of equipment and do 2 jobs instead of one!!
