I used to run SB8 in back and Karma up front. Never really likes the Karmas in front. They struggled for me on long fast sweeping turns.
My new setup is SB8 in the back and Crossmark in front, which I like much better.
I will try RR next time.
Note that this feedback is from Texas trails, never muddy (We don't ride muddy trails), mostly hardpack with some loose top.