Hi Ian, going back to the comments about using a rear macpherson strut-type suspension (or a front macpherson - used in the rear of your chassis). I just watched a couple of videos that helped me understand some stuff: Agent 47 racing's video explains that lack of camber control is one area where macpherson is not as good as double wishbone. The strut acts essentially as a sliding joint and the camber doesn't change much. The big angle on front macpherson struts is to do with scrub radius - and this is not an issue on the rear.
https://www.youtube.com/watch?v=ftf3KYHTOYU
/Drive have a series of videos explaining geometry. In episode 1 he notes that lopping 2.5" off a strut has a big effect on geometry and will be "pretty messed up".
https://www.youtube.com/watch?v=x0oi9SHJPvg
Camber control for grip, stability and braking is one thing but the other, as Ozijim points out in his post, is keeping the roll centre under control - if it changes drastically the car could get suddenly out of balance.
cheers
Ross