From the fixed gear mailing list: "Actually, medium is best. If you go too small, stresses on the drivetrain increase, parts wear more rapidly, and wheel slippage is more likely. If you go too big, it's just excess weight. Generally chainring sizes somewhere in the 40s are good." I think cogs under 12 teeth are theoretical arguments at best, anyway, due to the lockring clearance issue.
But the real issue is why the h3ll would you want to run 52-13? Are you Paul Bunyan?