How many degrees will a Stock 05' w/ Sport Suspension be able to dial out in negative camber? I am looking for -1 degree

Might be my next purchase Helix rear control arms and front camber plates

(Well did buy 15" Studded Pirelli Snow Carve on Steel wheels today from TireRack)

 

Stock 05' MINI will have small adjuster at bottom of lower rear control arm. Maybe a range of about 0.5 degree camber but you need to make right and left the same and the amount of camber you have now will depend on your MINI, the suspension you have, the weight of your options and your passengers/load, and any other suspension upgrades you have that might affect ride height (not rear swaybar).

Normally your rear camber should be about -1.0 to -2.0 and be within Stock settings. You can change whatever it is by about 0.5 degrees total. So if it is at -1.4 on the left and -1.6 on the right and your adjusters are about in the middle of their range then you can pick about -1.3 to -1.7 degrees with right and left matching.