I regularly bounce mine off the limiter at 6700 going through the traps. Not sure if its safe,I know it makes power up that high though. I typicaly shift at 6200-6500 on the first two shifts.
i have my rev set for 6800 however these cars stop makeing power and just flat line from about 5900 up to 6500 so there is realy no reason to shift higher thne 6000-6100 as you actualy have more area under the curve with the lowet shift point unless your runing a very steep gear..