So the aluminum insert, although having no face on the non-drive side, is exactly the correct width specified for the GXP bottom bracket. And even though there isn't any "height" to the face, the face was perfectly flat. When you snug the GXP up against it, the bracket does not damage or touch the carbon. It fit perfectly and I have had zero problems with 2500 miles since that upgrade to SRAM Rival. My apologies for not following up!