With 34" MT tires, once the flexy kit is installed, the tire will tuck up in there so much that it will catch the splash guard, which if you are moving at any speed, may rip it out of there, bending the fender all to ****.
I had mentioned this on the SFIFS thread, Bigmeat confirmed my suspicion that his had to be removed as well.
I don't often drive in gravel, and I am going to bed liner the inside of the fender, which is surprisingly rust free. That will help prevent dents.
She isn't a DD anymore, I drive the F250 and the wife drives the RS. Minimal road time=less chance for damage.