Pat,

78 will be fine and should equate to around 100 days. I tend to incubate at lower temps starting at 74 which results in 125-130 day range. Two years ago I had a Yellow Tail clutch go over 140 days and the hatchlings were not only huge but started feeding quite easily. YT’s typically lay for me late December early January. I breed them in July/August as they do in the wild.
I already have YT, Rubidus and Uni eggs in the incubators.

Alan B