• I assume that the risers sit on, rather than in the well?

    Yes, because my risers have a deeper chord than the stock ones.

    is a 2mm bridge adequate?

    Check your thread engagement, if there's enough to use a 3mm bridge I'd stick with that. The Mk1 had one set of converter plates added without needing longer screws.

    In the end, you're the one with the Mk2 bars in front of you, take measurements and see what will work.

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