Why would he input data outside the realm of what the sensor is designed to read? Genuinely curious why this would be a good idea. I haven't seen the logs but I'd guess they are reading a rich condition and would have him lean out open loop. The cells were built around a target AFR from the factory.
For the OP going wide band is obviously the way to go, tuning open loop with actual data instead of blind. Have a bung welded to the front header and report back what the spread is between fueling of front and rear for target AFR's, I think the "rule of thumb" being said is 20%.
My worry is for every 1 person willing to install and tune with a wide band there are probably 30-50 unwilling to go that far, adjusting the values in open loop off of data from a narrow band sensor I don't think is a wise decision.