When I switched to Lithium Polymer batteries I had to deal with the increased voltage, as I had previously been running at 4.8 volts (four NiMh cells) and the receiver and servos were not rated for the higher voltage, and may have been damaged by it, although robots have run at higher voltages before.
The pictures below show what the regulator circuit looks like, and gives a circuit diagram. Feel free to use this information for yourself, but the usual disclamer regarding the responsibility for any damage being yours applies.
The LM7806 voltage regulator can get quite hot, and will automatically cut out when this happens.. I bolted the circuit to the robot’s metal chassis and used heat conducting grease as well. It ran cool after that.
The AWS rules require an on/off switch. Using two pins attached across a break in the input voltage gives the opportunity of attaching a jumper switch taken from an old computer as the switch. It’s also extremely light.
I now have two of these circuits and whereas before, when I only used an LM7806 with no capacitor they burned out fairly frequently, since using the circuit they have been very reliable.