Ironically I have found the exact opposite with mine
Ran 10K front and 4k rear last night on a 50/50 mixed dirt and astro turf track, and found the back end was very loose.
Switched to 10k all-round in the diffs and the car was much better.
I also found that 10k in the front takes away a bit of turn-in, so am contemplating running 4k all-round for next meeting.