Control arms adjustments?

[osdmike]

Hi!

My friend wants to lower his Chevelle -66.(see pic.1)

The rear upper and lower C-arms are CPP,and it´s possible to adjust the uppers a little bit.(pic.2)

I´ve read that the link arms for a traditional 4-link should be adjusted:
lower arm = parallel to the ground
upper arm = parallel to the lower arm , for comfort/street driving.

Since the upper arms are shorter than the lower on a Chevelle,what position of the c-arms am I looking for? (pic. 3)

Any suggestions ?