This is exactly what suggested you to make with the current stopper plug and a piece of threaded rod+a nut !

A stopper on one side is enough.

You have seen the picture of my Birdy/fork, it has Big Apple and it works.

The R&M Birdy Rohloff come from factory with the same front light assembly and Big Apple and it of course works, below a picture of such a Birdy Rohloff:


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