More good progress today using your ideas guys, thanks
Bumpy oswestry track, tried the losi springs as suggested (red rear, green front) and also dropped to 25wt oil in the back (30wt in the front) and it was easily the best its felt! Also took a 2nd row of spikes off the outside of the front tires (plus a row off the inside) and a row of the rear outside too, and it enabled me to drive much more aggressively!
Looking forward to Eden park next week!