Guys:

A zener is what we used way back before they made BEC receivers. I used to race offroad electric and ditching the 4x AA battery helped lots. It was iffy if you ran a hot modified though, because your Rx tended to cut out if the car pack got too low... then again, car couldn't go too nuts too fast... and adding a failsafe board solved that issue.

Then Tamiya began making that add-on board that had one to go with their MSC's, and soon Futaba and others were integrating it into the Rx's.

If its your ESC that you are worrying about, why not power it from the Rx supply? If the Rx has BEC, it can regulate for the ESC, right?