lexm
Not sure what chain ring, cog setup you ordered with your ss Brommie. Mine was 54tx12t which was in the 70's gear inches. I found i wanted it in the 60's. A Surly cog slips right on(13t in my case) The Brompton cog has a spacer on either side,the Surly cog is a bit thicker so you would replace one of the spacers with a thiner one which all bike shops would carry. This way you get the chainline right. One tooth more doesnt require adding any links to chain.

Its tough waiting for it to get there huh?

Very neat looking Strida,by the way we have a dealer in town here and i have looked at them up close,quite unique.