Maybe just bad luck Spinedoc. This side does have a high turnover so sometimes I suspect posts get missed. There are several very knowledgeable people here regarding the testing of systems specifically with regards to Cats and emissions. I have had much help from those, so feel the urge to comment.
Several did post on the SL forum where you first raised your question, however I was also a little surprised when I raised a similar question here about aftermarket Cats - no one could recommend a replacement
Hope you find your new OEM Cat is really an OEM cat as that's a VERY good price. Dealer price here is GBP1500 = USD3000
Lea