Alot of people struggled with grip roll in the final, ( i know its a different car! ) I decided to change to a stiffer front spring for the final as I saw the grip coming through in the later heats, had an absolute blinder in the final after breaking 3 servo horns on the cougar through the day, from 10th to 1st
Best thing I know for grip roll is to stiffen it up, cut down spikes as you have, reduce ride height.
I'm sure people will give you alot more advice more specific to the x-6!