Yes you can adjust the guide. You get adjustment spacers for it but the instruction I got made me think it should be above the slider. Still lots of place for adjustment so run it as you like.
@norbar it looks from the picture that you could adjust the guide out a bit more as it says to in the instructions to have the ring be flush with the outside of the polymer guides
i havent run a gamut on my dh bike so i cant say anything on the toughness of the ring, but i have one waiting to be used on my super d bike. i have put them on others bikes, very simple. i live in the desert so thick mud is not something that i see. the straitline is also simple and the person that is using it is not a regular or hard rider but i am sure it will hold up just fine. i think they make some of the best pedals.
Straitline behaves great in mud. I rode it in wet mud, dust and mud so thick the tires turn into mud balls and you can't even walk, let alone ride.