Thanks for the infos.
I'm used to stop pedaling or even backpedaling when shifting gears on the Alfine 11, so it's no problem.
500€ for the bike,
200€ for the IGH, and possibly no need to change the rear wheel.
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Edit:
It looks like the Curve requires horizontal non-turn washers. In case
the washers provided by SA aren't for horizontal dropouts, will
non-SA washers work as an alternative?