All,
I would keep the voltage at 12 volts. All we need to do is use different spurs and/or pinions as allowed by the rules.
Here is what the different gearing looks like running at 12 volts.
stock – 9t pinion with a 24t spur = 7,875 calculated wheel RPM
option 1 – 9t pinion with a 23t spur = 8,217 calculated wheel RPM
option 2 – 10t pinion with a 24t spur = 8,750 calculated wheel RPM
option 3 – 10t pinion with a 23t spur = 9,130 calculated wheel RPM
option 4 – 12t pinion with a 26t spur = 9,692 calculated wheel RPM
As a point of reference, I typically run all of my well handling cars with a calculated wheel RPM of 9,100 to 9,400.
See, no need to change the voltage to anything other than 12 volts. Everyone just needs to find the gearing that works best for their skill level. Run the gears that you can run to achieve the best results. More is not always better. Better is having a car that is drivable and stays in the slot.