Monkey Nuts are for pushing the axle back but still keeping it stationary when you're using a geared setup on the KM. This keeps the rear wheel out of the front derailleur when using fatter tires. You are running a fixed Steamroller; just add a link or two to your chain and slide the wheel further back in the dropouts. FWIW, a half inch or so of wheelbase will barely be noticeable. Your Steamroller is twitchier than your cross bike because the 'roller has steeper angles and tighter geometry.