"Safe" AFR

I thought that the ideal AFR for the coop was 11.5:1 and it's a good idea to stay as close as this as possible, however, over on the PerfectTouch thread, there's a report from an experienced FCCUK'er that he's running up to 12.8:1 and doesn't seem too worried? Is 12.8:1 OK?

The reason for the question is that my AFR was going to 12.8:1 at 1.2bar and this was considered dangerous by an RR guy. It's worth noting that the car was also deting? If my AFR was still 12.8:1 and it didn't det would this be considered "safe"?

To be safest it should be on the rich side rather than the lean side - i.e. 11.7-12.3:1 for full load.
My car runs at 12.1:1 or richer on full load.

Thanks JohnS.