Wouldn't the safety window depend largely on the EGBP? I don't notice such swings in EGT when I'm playing with a lot of the bigger turbine turbos like the 6266 and the 35r as compared to a 60mm turbine on the 30r or a stock location turbo with a smaller A/R, which I try to keep to the guidelines that you both suggest here. I noticed that most of the larger turbines and a/r turbos drop egts too much below 11:1 to the point where I need to increase timing to bring torque back up. I've found that 11.2 or near 11:1 seems to produce a bit more torque on the larger turbines. I do try to stay below 11 if the car is running some type of 63 housing or some strange hybrid turbo.