Hi,
I think you would have more chance of a good response in the gimbal section, but I will try to help you. I have another model of gimbal which also uses the same motors and the guy who sells my gimbal recommends only 3S or 12v. The motor itself may be able to take over 14v but your board probably won't. For a 5D, you're probably on the limit of this motor's capability so I'd try to tweak PID settings first before jumping to a bigger battery.
Best of luck