That would be true for nitro using a 2s lipo receiver pack, but he is running electric so a BEC is needed to get 7.4V to the receiver. I guess technically you could use a 2s lipo Rx pack in an electric setup also but it wouldn't make any sense as a BEC is smaller, lighter, and you already have a voltage source powering the car that can be used. But either way yes the Spektrum receivers have no issues running on 7.4V, mine has been working fine.

Adrictan, installing an external BEC isn't a hassle at all. Just need to add a set of small leads in parallel with your main battery input. I take those small wires into the BEC at 14.8V and plug the other side of the BEC into the receiver which outputs 7.4V. It's mostly a matter of finding where to mount the BEC and how to run the wires cleanly. As you can tell my wiring isn't that aesthetically pleasing!