If you mean use the recline function on the seat then no you should not use these rearfacing. rearfacing has the one angle and it locks in that position....Also it will affect the ability of the rebound bar to sit perfectly flat against the back of the seat, actually I am not sure if you can alter the recline without disabling the rebound bar even? hmmm......not sure on that one. BUt IMHO not worth the risk.....
Our seat doesn't have a rebound bar, so there was no issue there for us, I didn't take that into account when I made my original post. I definitely wouldn't be trying to modify or remove parts of the seat at all!! Also would definitely not be using the recline for FF for RF. Definitely not worth the risk!! The mirrors are great