Read again.. I was referring to a different design..



Chuck a cut off an Old square taper BB spindle in a Lathe. Mount the crank on it. and machine off the shelf if you wish . to get it good and Flat.
a decent machine shop can do that in an Hour.

Stronglight also Supplies the cranks that Brompton uses to assemble their bikes
people have been Bolting a granny gear on the Outside of the Older swaged 50t Brompton cranks , with greasy finger shifting whether the granny gear is inside or outside
doesn't matter, they just took off the plastic trouser guard.

you may be happier with the offset types .. they have been around from various sources for a while, ... Happy Shopping..