I responded to your post at Lateral-G. Shoot me an email if you still need help!



Don't worry a whole lot about the rear sagging, most of the support is done by the quarters. The rails in these cars really don't add much support, I suspect most of their purpose is to positively locate the rear spring eye. You'll notice a big difference when switching from the 2x3x0.040 U-channel (yes, .040" thick), to a 2x4x0.120 rectangular tube...a healthy increase in stiffness!