How does the silence interval work in stepped sine mode? This seems like a poorly conditioned input as we have to know the measurement period in order to know what silence interval we want, and we shouldn't really need to do that calculation in the first place.
What makes more sense to me is a duty cycle. So for instance if I have a 300W amp with a 30W heatsink (or a 30W PSU), I need to do testing with a 10% duty cycle in order to not overload.
Instead of a duty cycle maybe this should be an average power input. So at 0dbFS, if I want 10% max power, the duty cycle would be 10%. At -3dbFS, power is halved, so duty cycle should be 20% to achieve the same average power output. This approaches what is called isothermal conditions, as the average temperature does not change.
Secondly, if this is used to avoid average power limits, then the measurement interval is a critical number. A unit might survive a 1 second measurement interval but not a 4 second one. So the measurement period MUST be known. Also for this reason, averaged measurements should be broken up into individual test/rest periods, so the test periods don't string together into an unnecessarily long period.