For 1s I use the Hobbywing just stock (17.5 stock class) with a futaba 3pm radio without a booster or extra battery. the reciever works fine down below 3v and I never get below 3.5V at any time on my races. (8min)
The only issue i had was the older AMB transponder was not super accurate down at 3v it worked but occasionally I lost a lap. so I switched to the newer 2 wire Small form factor amb that can go down to 2.5v without issue.
Just make sure to use a fast servo as with lower voltage the servo goes slower I use a .05 per 60deg