Boomer,
Not flashed yet to my knowledge and I have to say that you are correct, totally different bike once the needle swings past 6000 RPM.
I have yet to explore the higher ranges of the Tach but i really would not want to give up any of the low RPM rideability that I am enjoying.
The flash I have (Shoodaben Mountain Runner Premium)
enhances that low rpm grunt (up to 20lbft at low rpm) but for me the biggest gains are the huge improvements in on/off throttle transitions and in predictability. They give you the confidence to get on the throttle sooner when coming out of a corner as you know what it is going to do. Smooth, predictable, and silly fast if you want. Yes, there are minor gains in high-rpm power, but not many of us spend much time up there as it's not a race bike for most of us.
When I am out "playing" in the twisties I tend to be in 2nd or 3rd gear between 4000 and 7000rpm as that is all that is needed for 20-80Mph.
On track days I use 1st to 4th at 4000-9500rpm which is good for 140+
On busy roads I tend to go with 3rd gear for 30Mph, 4th for 40Mph, 5th for 50Mph and 6th gear for 60Mph+.
Smooth and rapid enough for real world traffic and roads, but with warp-speed always available with a brief flick of the left foot and right hand.