Che ,
I find having 7 degree caster on the frt 6.0 frt c hub gives you more push where as the 5 gives you more steering.I uses the aluminium 5 degree c hub for reliability and strength.In your case use the 5 degree hub.Our track is high grip and bumpy.I uses frt diff one ways and center shaft pulley.Cheers.
Chrisman