Looks like my prior post has a problem, I can't see it anymore, so sorry if this is a repost.
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So nice to find a bunch of fellow A9 riders! 

All my riding buddies are like Why? I built mine in Nov/Dec 2020. I have more than 3500 miles. 6? races. 1 crash at 39mph and only a minor scratch to the bike...

my build is XL, Hb017. ultegra di2, quarq pwm w duraace chain rings, toseek carbon saddle, tokyo wheels epic 3.4, shimano ultegra pedals, DT Swiss through axles,
since the pics I've removed headset spacers and cut stem more and put in specalized rib bottle cages.

I've struggled with a creaky headset. And my saddle rail clamps allowed the saddle to creep on 2 different saddles but I think I've fixed it by painting a tad of epoxy with skid proof mixed in on top and bottom of the rails. I maybe should have gotten the L and I'm 6'2". it's a big bike. handles very well. super smooth and stiff. I started riding this bike at 220 lbs weight but I'm losing weight, down to 194 so far. Great bike.

I was new to building fully internal integrated hydraulic. Routing cables in the handlebar was very difficult for a first timer. I also goofed and cut the steerer to short but Doris at Ican was like no problem and sent me a matching replacement for like $120! I will say on routing don't worry so much about dinging and kinking the ends of the hydraulics lines. Remember you will be cutting that part off anyways.

I bought these micro shims and cutted 4 or 5 of them to adapt them to the space over the headset.. Now I' m thinking about doing a shim cutted by a 1 mm Iron shim by a friend of mine that works metal for work.

Can you explain what problem you solved with the shim? I cant get mine to not creak a bit. I wonder if this would help