Just something I've thought about and have no idea how successful it would be but...There are always two 1/16" shims on a standard SA driver. Two 1/8" cogs should still leave room for the circlip. Between dished and flat cogs, it might be possible to set up a dual cog derailleur system with the standard driver and cogs. If you used a FW or S5 hub, you would have a ton of range.
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