Geoffrey, I run with nearly zero rear camber on my Satria for daily use, around -0.3 to -0.5 degree... But when taking the car down to track, it'll be set to -2 degrees, which I still believe it's insufficient to ensure flat tyre patch contact under cornering at the track... Beauty of these independent rear suspension set up... both the camber and toe can be adjusted...
On my E36, rear camber is set to almost the same as the front, my car is lowered, so the front camber is a bit high (still less than -2 degrees though) since I don't run a camber plate. For fuel economy, follow the recommended alignment specs... you can get it off any self-respecting service manuals.