you can run a Singlespeed cog on a 'Fixed" side. seeing how you wouldn't be applying any back pressure to stop. Even if you did pedal backwards since the cog is freewheel it wouldn't unscrew. Not sure what the motive on the shops part was. Has far as the Deep V's with Phil wood hubs I personally think that is a better setup for a sputnik than some cheap Alex rims. (sorry, I'm not a fan of Alex rims) Besides if your in the City esp. NY you'll appreciate the Deep V's more.