Good news.
The changes I've made to the shocks and camber link geometry cured all the oversteer and twitchyness of the car. It is now a car more than capable of fast laps while being easier to drive. If it is as good as any current car I don't know but will find out soon. Small changes from the stock TC6 setup, mainly shocks mounted in on the arms (for a 50:50 weight bias), kept the lower arm positions from the stock TC6 setup (vital!) and front camber link setup of the TC7 and the rear one is one hole longer (out on the rear upright).