What kind of cupholder mount is that and where did you get it? I've been looking for that style (that automatically adjusts to the drink size).
Also, they don't adjust. Those are just foam fingers that surround your cup- but they do hold a big gulp... Anyway, any GM fullsize with a 40-20-40 front seat should have come with it, otherwise they just attach to the bottom of the center seat if yours is missing.