Thanks Paul, very helpful. My challenge now is how best to remove the old pivot shoes. You can see in my earlier pic with the old shoe that there is a black plastic ridge that runs vertical attached to the aluminum frame. This ridge piece is pretty solid on the aluminum, but is seems like it could be pried away from the aluminum at the bottom enough to get the pivots swapped out. Do you think pulling it back on the bottom a few inches is the way to go or should I leave it in place and consider making cuts?? I don't want to pull it out without being sure I'd be able to get it snapped back in. Thanks.