Originally Posted by TryHard

1.5 splits on the front, 0.0 one piece on the rear. I lnow Kerswell ran that at the Cotswolds nat, gave more steering.

Now the 'dumping' theory. Basically any tire only has a finite amount of grip, with our cars, this is generated mostly by weight transfer (rather than say, aero).
As you correctly point out, generally making the car roll more will make it grip more, but only up to a point. Basically, by rolling too much, it puts too much load in the tyre, which then gives up it's grip.. This is the 'dumping' sensation I mentioned.
Bare in mind, the rate of roll also has a bearing as well as the overall amount. What I mean there is a car that rolls lots, but does so slowly (say heabily damped, or just a v.smooth driver!) would be able to hang into its grip more than say a car that rolls less, but does it quickly (lighter damping, aggressive driver).
The symptoms you mention are pretty indicative of roll too much, as the mid to exit of the turn is (usually) when the rear is most heavily loaded, and hence closer to its peak of grip.

Something else to look at would be going to a softer rear spring first, over a roll centre change.

HiH
Ed