MetalMan can make you a centerdiff drive unit that will work on the FLM and GorillaMaxx 3906 chassis- may require a little trimming/clearance work on the inside of the chassis rails to allow room for spurs bigger than 44tooth I believe. No slipper with that unit, but the centerdiff acts as one in a manner of speaking..
I like sysmetrical too, but one must learn to embrace the Asymetrical sometimes
