Problem has been resolved
Actually, no, that isn't what I wanted to do. If you look at the rules I wrote, You'll see that I wanted to rewrite 3 domains to match the canonical domain. It turns out that if I set the rule to final (add an "L" flag) it completes processing on the canonical redirect before applying the SEF rewrite block for the CMS. This will work provided my rewrite block appears before the CMS block.
pretty cool, but is it dangerous?
That's pretty slick, but is there any danger of it redirecting traffic you don't want to go there? Obviously, you couldn't use a ! operator if you had to contend with http and https requests...