Are any of the top caps listed above, absolutely flat from the bottom side too? (Basically just a piece of flat carbon)

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PoP.

slightly OT....

No top cap, expander.

saves weight, and its free

I know but I'm too pussy to leave the expander off...

I'm using a Colnago expander for Star forks that's a very tall and heavy one, extends below the upper headset bearing:

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That is because of the Acros headset. It creates the tension on the bearings from the bottom of the stem not the top and so the top cap is purely decorative. You could use an Acros top cap once you have tensioned the headset and tightened the stem. You could also get the Tune one that, like the Acros, is essentially just a plug that sits in the hole and isn't functional.