arm out the window:
The problem with engine failures in the hover is that invariably the real ones take people so much by surprise that there is no time for lowering the collective, even slightly (that's not just my personal experience, but also everyone else I've talked to who has had the same misfortune).
So training people for 'mid' and 'high hover' engine failures with something other than just being able to raise the collective is slightly misleading.
Certainly for certified helicopters, the low hover height for the HV curve is tested only with raising the collective.