Realising that this will p**s on Rudolf's parade, please avoid Savox servos in 12th. I've lost count of the number of "I've got a glitch/shutdown/brownout with my car... Savox servo..." posts I've seen on almost all forums, and the common denominator is the Savox. I've no idea why as they seem to work fine with 2S set-ups.
There's a reason why Futaba 9602/9650 servos are thicker than bugs on a bumper in 12th cars the world over - they fit, they work, they are very accurate and they are bulletproof. Far better to buy a second-hand Futaba (9602 if you have an analogue radio system; 9650 if you have a fully digital or HRS system) and never worry about any radio issues.
Try a wanted ad on here and be prepared to pay around £40 for a new-ish one, less for an older model. Expensive? Yes, but if you want to sell it on you'll get your money back. HTH
