The case screws are M6's. I used to go 80 in/lbs on them but have reduced that to about 72 (6 ft/lbs). The clutch spring screws are also M6's, well at least the threaded part is, so you use M6 torque values for them (6 - 8 ft/lbs). Don't go 12 to 15, that would be way too much.