It would be unusual to advertise a servo as being HV and not be able to run straight off a 2 cell lipo, after all that is the whole point of HV. Hitec's website says they run from 2 cell lipos and makes no mention of having to regulate them. The torque and speed are quoted at 7.4V but that is just standardising the specs at a battery's nominal voltage, all brands do this for all types of battery, for example quoting the specs at 4.8V but any 4 cell nickel battery will be well above 5V much of the time, it doesn't mean you have to regulate it down to a max of 4.8V. Other brands of HV servos also quote the specs at 7.4V but state their voltage range is up to 8.4V

I can understand a voltage spike burning up a servo but not a voltage sag, can you please explain?