I've been driving my RM-01 for a while with the 380 sport tuned motor and a 2-cell Li-Po battery.
The car is way faster then a M-05 but the higher voltage is actually overkil for the 6.6V 380 motor.
You can't use this combination for 5 or 6 minutes without overheating the motor cause of the higher voltage of a 2-cell Li-Po battery.
You'll get the same effect as when the Xray M18 had it's glory days, people used a 6V motor with a 7,2V battery for the extra speed but need to replace the motor quite often.
I wouldn't recommend this combination, it's better to invest for a cheap brushless combo in combination with a 2-cell Li-Po battery that has the same dimensions as a 1-cell Li-Po battery that's been used for 1/12th scale racing.