2015 Roll center - I am very very very confused

[dibble34]

Right, loving the 2015 spec but these new +2 rear hangers have opened a right can of worms for me. I have read up and read up and these are my findings so far

Running the +2 with no insert under gearbox = lower roll centre. According to hudy setup manual a lower roll centre should be better in high grip. However according to xray the insert under the gearbox should be used in high grip however this would give a higher roll centre and according to the hudy book a higher roll center should be used in lower grip conditions.

I personally find that lowering the rear camber link on the tower in low grip improves rear traction, but this is making a higher roll centre so goes against what xray are saying about the gearbox insert being used in high grip as this also raises the roll centre which they say is for high grip.

Can anyone explain/help a very confused average driver