Mr Tiger, maybe we can use a different axleTiger6 wrote:I'm only going to use the WPL motor, leaf springs and JJRC axles (and they will have to be cut down and rehoused).

Leaf sprung variety with WPL internals, i can maybe sort you out for adjustable width axles.
Or maybe we can look at designing a new axle casing to take the jjrc internals. they are reasonably strong, but only if you replace the nylon bearings with metal ones to ensure a good tight mesh. My experience is the jjrc axles only fail because the pinion has alot of play in the nylon bearing and it causes it to slip under load