What 1speedy says is exactly right.
High voltage servo's and receivers can do just that .... they can handle the high voltage LiPo battery's deliver.
Be careful though that you check out your receiver, to make sure it can handle 8.4V.
I had High Voltage servos
then realized at the last moment my reciever will not handle the higher voltage.
So I got a Regulator that brought down the Voltage of the LiPo from 8.4V to 6.5V
At this voltage it was ok for my receiver and any 6V servo's I would use also.
Regards,
BM