Nice conversion.
Now either use the outer chainring and push some gear inches, or take it off. You don't need a circular saw blade gashing your leg open when you wreck. While you're at the bike shop getting your cog/lockring tightened, get a set of single-speed chainring bolts ($5 - 6) and the tools to install them (http://www.comcycle-usa.com/ProductInfo.aspx?id=1800687 and and allen wrench).