FYI on the scale speed of the Leopard. The HL pot metal gears are really really slow and don't do the Leopard any kind of justice at all.
well so happens I have a set of black steel gears and 400 motors.
I loaded the motors and gearboxes into my Leopard, battery is not a factor here and I am using an RX18 2.4ghz. No other modifications were done to the leopard.
I calculate the scale speed of the Black Steel Gears and 400 Motors to be 39.78 mph over a distance of 90 feet so this should be reasonably accurate. this was flat pavement with no obstructions.
Max speed of the Leopard 2A6 according to a couple sites is 45 mph on Wiki and 42 mph on Today's Army.
Needless to say I think I have found a good gearbox for the Leopard 2 at $49.00 a set, I am pretty confident that adding a Clark board and a Walterson Gearbox you will be able to tweak right into the 44 to 45 mph zone on a scale speed.