This does suprise me.. this car is awesome..has loads of rear grip.. and ive never struggled with lack of it!
Worksop and Chadderton.. the car is perfect and they aint the grippiest of surfaces..
The RB6 in my mind has everything... ive tried and run different cars over the last 12 months and always went back to my old MCS... but now since ive had the RB6, ive retired my MCS to a shelf queen as the RB6 is now 1st choice.
You need to drive one yourself and stick with it how it comes out of the box, dont change shocks to the small bores.. as the Big Bores are in my mind the way to go.. Ive heard that others have tried them without success.
You say about modding rear wishbones?? you can adjust wheelbase both inboard or outboard, so should be no need to modding wishbones?
If your looking for set up advice etc, send me a pm, or indeed point the people who are struggling my way!

Cheers
Nick