Well, you could lower the voltage a bit I think by using rechargeable batteries. 1.2V as opposed to 1.5V of non rechareable perhaps. The other thing is alot of work but it has worked for me on a 1/24 Nashorn I am building from scratch. If you can get your hands on a forces of valor parts tank and remove the control board soldered to the motors and resolder on the vs motors it will provide poportional control and the king tiger should be able to to almost a crawl. Don't use the FOV motors and gear box as they are not as tough as the VStank motors.
Greg