Now, why is it so hard for muffler shops to understand this? I've got a customer coming back and forth because a muffler shop down the street is giving him bad information. Bunch of numbskulls out there, I tell ya.
What if the o2 sensor hole is damage? And they mounted the o2 sensor down another 1". That's still fail? That would sucks..
If there was room to move the oxygen sensor down 1" from it's original location, I'd do it. I'd install a replacement bung like this one.
http://www.amazon.com/O2-Sensor-Bung/dp/B004X2ALG4 As long as it is placed between the cats, I would have no problem with that installation.
The original question was if I would allow someone to install an oxygen sensor onto the body of the cat itself. I would visually fail that cat.
Why make it simple, when it will work equally as well complicated.