More often than not, i have the rear seats in the flat position (better visibility & i have a massage table in the back), and i would like to know if the Schroth's can adjust out to that, or if the rears need to be in the up position.

 

From my experience, they need to be up, that's the way they were designed. I haven't tried threading the clips around the seatbacks in the down position. I guess it's worth a try, though I'm not sure about it for safety reasons.

Though if you run with them up, just make sure they are securely latched. Halfway into a track session, the seatback flipped down under hard braking and the Schroth just about choked me....