Of course it depends on the track but my goal would be to drive 10minutes with T-2060 pipe. If the heatss are 10min or semis 20min then you have to be able to drive 10min stints if other guys can do it
I've tried 5.5mm with 28XZ engine and 21J carb and it really lacked power for my truggy. It was impossible to drive with it.