GuyKilfoil

Mine was super noisy too (like a big crack every time I hit a bump) but I got my LBS to follow the Cannondale work instruction for the seatpost to the letter and it's been perfect ever since. You can download it here: https://www.cannondale.com/-/media/files/manual-uploads/manuals/019_137369_oms%20my20%20supersix_en.pdf Check out pages 15-17...

That's a pretty impressive weight. My Disc Ultegra quite a bit heavier in size 58cm (around 1.1kg more)... But no mods so far. Going to change bar, seat post, crank set, disc rotors and put on that Soigneur internal cable routing kit over time. Bog standard for the moment but it's an impressive machine. I love it!!

What have you got the weight down to so far? I'm assuming you're planning on ditching that heavy standard bar and stem and opt for the carbon seat post at some stage?