Another idea is to take magnesium before bed, because it relaxes muscles.
You could try non-RS prebiotic fibers like konjac (e.g. shiritaki noodles) that will still feed the gut bugs. I'm not sure if you can totally substitute non-RS fibers and get the same benefits, though.
I would love to know how RS would affect muscle tension. Since starting RS a few weeks ago, I've noticed a welcome tension in my abs...it's like I want to sit bolt upright in my desk chair and am "aware" of my abs when walking, bending, etc. It may be unrelated but though my weight remains about the same, my waist has shrunk 2 inches.