Okay, why don't we stop talking and start trying 4 or 5 cells.
If we are such experts on this issue it shouldn't be a problem to spend a day trying 4 and 5 cell configurations at the track.
I guess it would make more sense discussing this topic if we have really tried it.
Especially the sponsored top drivers, they have lots of equipments to test the cell limitation.
And while you're at it, give 6 or 7 minute racing a try as well. This way you won't go for 5 turn motors.