Setup for slippy surfaces?

[orinoco]

Has anyone had any joy with a setup for low/medium grip surfaces with the S401. I was at Worksop yesterday for my first run with the car and struggled to get anything near a solid setup. The problem being the car hooking round corners both on and lift off throttle. Tried loads of changes most with no great effect. I was running saddles with 60g of weight behind the saddles, under the gearbox supports. Front 1.5mm anti-roll bar. No rear roll bar. 400cst losi yellow springs rear, 425cst losi black springs front.(does anyone know the poundage rating of the Sworks springs?). Kit 3000wt oil in diffs(not enough time between rounds to change due to running 2 classes, would have tried heavier front oil given time). I tried a multitude of changes to roll centres etc but at best I was struggling to put power down due to the lack of weight over the rear.
We predominantly run on a mix of slippy wood and carpet and really need to get a locked in back end for such surfaces, any ideas?
Car seems pretty bulletproof and good to work on and I really like the engineering designs this brings to 1/10th offroad, just need a setup. Cheers.