Thanks for the info. I may have the same problem with my front shocks. We weighed all four wheels when most of the parts were on and I think the front is 500 - 700 pounds lighter than the Mustang II. We also lowered the front roll center, so I think that would require an even softer sway bar. Your experience confirms my thought that Mustang II bar would be way too stiff.
My goal is to have a canyon carver that could navigate a road seam without launching it into the next lane.
I'm planning to make the mounts and build links that can lengthen or shorten the arms. However, there are so many choices in sway bar spring rate, I'd like to get close to begin with.
And I'd like to understand the mechanics well enough to be able to make some sort of educated guess.