It's been over a year since I got this project done, but I just did some related work and thought I'd share. I wanted to know what my swaybar spring rates were, so I measured it.
I had to try a couple different methods to get the swaybar figures. What I ended up doing was bolting the bar mounts to some square stock and clamping that to my workbench. Then I attached the end link to another piece of square stock and set that on a bathroom scale. Then I took a piece of pipe, put it over the free end of the bar and moved it down one inch at the appropriate end link hole and read the scale on the other side to get the bar rates.
What I came up with was that the front bar has a min rate of about 105 lbs/in and a max rate of 120 lbs/in. The rear had a min rate of 50 lbs/in and a max of 80 lbs/in.
I don't know why, but I was really expecting hundreds of lbs of force there. I was pretty surprised at how light the bars are.
Again, these started life as the MSA front bar and the ST rear bar, with all of the modifications listed in this thread for adjustability. The rear bar is surprisingly adjustable, and I was pretty shocked that I could almost double it's force by adjusting from the lightest to heaviest setting.