Originally Posted by fietsbob

nah just leave the disc Off .. Steel frames can be bent inward and spread, aka "cold setting"

people do that to stuff in new wider wheels in older frames

You might also be able to add some spacers to the left axle , limited by the axle lenght available of course
building the wheel to be centered between the 2 over lock nut ends..

Buying online is a bit of a handicap in measuring things.. the Company website may be more informative

Sturmey Archer