The centre diff has 2 parts. Epicyclic gearing to give the split and the viscous coupling to transfer drive when the is a speed difference front to rear. I could get a stiffer viscous but that won't change the torque split and would likely burn out as I get so much slip/ speed difference.
I could put an LCD in the front to stop the one wheel spinning but likely would get both spinning instead as there's no weight on the front, giving more understeer.