The problem is the receiver and servo need at least 4.8v to operate. most ESCs do not have a step-up voltage circuit from 3.7v.
I suggest you to look into a LiFe receiver pack. It's very small and quite light. it has 200mAh and can last 2 rounds of driving, and it is quite cheap too!
When at full charge, 2S LiFe is 7.4v. All you need to do is discharge 10mAh or so, the voltage will drop to about 6.6v. (I have tested with a volt meter) I tried it with KO receiver and servo and its 100% ok. Just remember to discharge a little before use.
@200mAh, 1 - 2 runs, no problem.
Just charge the LiFe when you are waiting for the tire compound to dry. Since it is LiFe battery, you can use 2C or even 3C to charge.
Bro lung, here is the link for 1s Lipo BOOSTER: http://www.tqcells.com/
If you like it, I have 1 brand new with me, I go TRC on this Sat at about 6-7pm, Room#7!
Alternatively, you can consider LRP Stock Spec, it supports 1cell.