HI,
How different are your runtimes between free running on the track and final races. I clocked 9:30 minutes runtime on free running on track . Laptimes are around 40 seconds. Would it be playing too safe when I set my buzzer 7:30 minutes and pitting at the end of the lap ?

you will never know till ya try it?

Best way to judge is from measuring fuel after qualifying. If you have half a tank of fuel after a 5 min quali you would be safe for 9 minute pit stops and maybe even 10, etc, etc. just remember you should minus about 2 minutes from your total tank run time to determine a safe pit stop strategy.